US2661798A - Flare stack, pilot burner, and pilot igniter - Google Patents

Description

Dee- 8, 1953 o. l.. cLEvENGER ETAL 2,661,798

FLARE STACK, PILOT BURNER, AND PILOT IGNITER Filed Nov. 12. 194e F'lG. 3.

FIG. 2. WML/wd'. ffl/W Patented Dec. 8, 1953 FLARE STACK, PILOT BURNER, AND

. PILOT IGNITER Oliver L. Clevenger and William A. McElhannon, Baytown, and William W. Jones, Houston, Tex., assignors, by mesne assignments, to Standard Oil Development Company, Elizabeth, N. J., a

corporation of Delaware Application November 12, 1948, Serial No. 59,662

2 Claims.

The present invention isdirected to an apparatus which is suitable for igniting combustible mixtures. More particularly, the invention is directed to an apparatus adapted for use in connection With pressure releasing systems in Which large quantities of combustible fluids are suddently released to a flare stack.

In the petroleum refining industry a number of processes operate under elevated pressure. For example, in thermal polymerization in which propylene and butylenes are subjected to high pressure and high temperatures to cause polymerization thereof, it is sometimes necessary to release the pressure suddenly and to discharge the contents of the thermal polymerization unit. When this happens, large quantities of gaseous Vand liquid combustible mixtures of hydrocarbons must be carried away from the unit to a safe distance and ignited. Otherwise, large quantities of hydrocarbons would be released in areas where they may be ignited to cause dangerous fires. In catalytic cracking and other cracking operations such as those of the thermal type, itis also neces,- sary at times to provide some pressure releasing means which usually have included elongated vertical stacks located at a distance from the unit. Locating the stacks at a distance from the unit is not a very good solution to the problem since the pipeline connecting the flare stackvto the unit may cause delay in igniting the released uids and, therefore, build up inV the areas immediatelyY surrounding the unit a dangerous combustible mixture. Catalytic cracking operators usually provide, adjacent the catalytic cracking unit,

elongated stacks some '200 feet in height which allow the ready release of the unit to the stack Where pilot lights are available to cause immediate ignition of the released material.

I and satisfactory ignition of a gaseous mixture However,

the diculty exists of maintaining the pilot light would be possible to protect the pilot light and to keep it burning at all times to make it available for igniting the combustible mixtures. However, to maintain a pilot light at the base of the stack presents a hazardous condition especially when the are stacks are located adjacent a catalytic cracking unit. When the pilot lights are located adjacent the upper end of the ilare stacks, it is difficult to maintain them in a lighted condition in view of the Winds prevailing at the elevation of 200 feet or more to which the flare stacks usually extend for safety purposes.

To emphasize the seriousness of the situation in maintaining anelevated pilot light vavailable involving an elongated vertical stack orV conduit issuing from an elongated :Hare stack.

Another object of the present invention is to provide an apparatus suitable for igniting a combustible mixture issuing from the top of a vertical elongated conduit,

The objects of the present invention may be achieved by providing in combination apparatus l which includes an elongated conduit having located adjacent an open upper end thereof a suitable burner mechanism such as the conventional burner available on the market provided with a shield which protects the burner and also serves to denne a passageway for conducting the flame.

The burner should be provided, of course, with a source of a f reev oxygen-containing gas or air and a suitable fuel source. The elongated conduit communicates at its lower end with thesystem from which Vpressure is to be released. Such systems will include a catalytic conversion operation such as a catalytic cracking operation or other'high pressure units ina petroleum renery such as thermal polymerization or cracking units,

distillation operations which are conducted under pressure, and any of the numerous processes available to the renner from which large volumes of combustible mixtures may be released. Located adjacent the burner is an ignitionsystem including an electrical resistance element located in the path ofa mixture of a combustible fuel and a free oxygen-containing gas or air. The igni-v tion means allows the ignition of the combustible mixture in the igniter which in turn will ignite vthe combustible mixture in the pilot light andy also serves to keep it burning at all times. The resistance element is energized through suitable electrical conductors-connecting to a source of electrical energy.

The invention may be described briefly then as with its lower end in communication to the systernfrom which pressure may be released and having an open upper end which is provided with.

`apilot burner` adjacent the open end and a pilot y 3 burner igniter. The pilot burner is provided with an independent source of fuel and is so designed as to allow formation with the fuel of a combustible mixture with air. The igniter is located adjacent the pilotburner and it 'includes ,a conduit whose open upper Yend is located .adjacent the open upper end of the vertical elongated stack and adjacent to the open passageway dened by the burner. At the lower end of the ignition means a conduit is provided dening a passageway in fluid communication with a source of fuel. This conduit is surrounded by .a larger conduit provided with passageways or inlets for admission of air for admixture with the fuel introduced into the ignition means. The mixture then viiows across the resistance element which causes it to be ignited when the resistance .element is .energized.

The invention will be illustrated by reerence to the drawing in which:

Fig. l is a iront elevation of a device in y'accor-olaioe the present invention including an elongated ver-tical conduit, a burner and an igniltio'n -for said burner;

Fig. 2 shows 'a 'detail oithe burner, the ignition means, and the arrangeirient of the two in vcoinbnation with the elongated vertical "conduit iadjacent the 'upper end thereof;

Fig. 3 is "a view looking 'downwardly on 'the device 'of Fig. 2; and

Fig. Pi Ap're'ser'its a detail of the construction of the ignition means.

Referring n'ow lto -the drawing, numeral I I designates an 'elongated 'vertical conduit such as a flaf l"stack of va 'catalytic cracking unit. The

bu and cnfieetuthereto by a plate I6 isA an 'lgniicrlv yra'rrs =I-'I `lenix'i'g 'a conduit 'whose `kapen ne discharges adjacent the lpilot bu'ier l 3and:icmnected thereby by plate I6. Thefiowr 'end Aof the passageway vdonned by ignitin'rnea's `I .cniiectsfintofa smaller conduit I8 diiiigfa 'passageway in communication with a ignition means I 1 projects upwardly into the por-A tion of ignition means I'I indicated by the portion 25 which is provided withperforations or inlets 2t which allow air to be admitted into the region adjacent the extension of the vertical conduit I'B which is indicated by the numeral 21 The electrical conductors I9 lead into ignition *means I1 through lead in boxes 28 provided with insulating bushings 29 which are constructed to withstand a temperature of about 2000 F. The electrical conducting means I9 connect to resistance element id which provides a source of heat i'or vignitiiin of the combustible mixture formed, the passageway defined by the ignition means i1, by admission of fuel from conduit I8 and air from perforations or ports 26.

When operating the improved device of the present invention, it may be assumed for purpose of illustration that the unit to which stack II is connected has to be released suddenly and valve 43 is opened oor'in-ecting the unit being Trelefsed by line 'I2 torstack I I and providing a sudden lsource of combustible mixture. Under these conditions, to be assured that the 'admixture is properly ignited 'at the'upper end M oi stack II, fuel should be 'flowed through lines I5 and I8, irespectively, to the pilot burner and to the ignition means; eiplosionfproof switch 2l connecting the ignition 'means |19 to a lsource'of electrical ener'gy 'would be closed 'thus energizing the 'resistance 'coil 24 'and causing it to be heated to a 'po'iiit where it will ignite the 'mixture of Vfuel gas and air passing vover i't. fheignited 'mixture issues from the upper 'en d of the passageway defined' vby 'ignition means i i 'and 'immediately ignite's the pilot light which in turi 'causes ignition of the combustible *Huid issuing from vthe top 'Cif iaiie stack 11. f

centena e ein te segnati@ to the piiothurner ignited at `r-all times. It will usually that "the pilot light blown out by high geometricalntshow'nwmeh may be thefsame Y fulfin;commuicationwith'thepassage# iin dly'conduit I5; Connect-ing into the igii nineties *n atea point above me juncture there ith ofconduit V8 -is electrical connecting "-l'f which is evidedwiih a transformer es and an explosion-proof switchl.

5 erringnowtoli'g. 2, theburner Iljis located adjacent thetop'ofstack I'I as shown and is provided withiaconduit 15. Adjacent the burner Il is iition means l1 Whichi's Ycoxinect'edto burner i4 byplate lI8 allowing the passageways by'bi'irner l:Iii-and ignition means I'l-to discharge atfafpv'oin't slightly above the openend oi Astack II. BuriierA lincludes va jet 22-through which the 'fuel admitted through conduit l5 is uiseharg'e'dtriefemanalmans indicatedlby 2-3 which may be perforations in burner Il *forY-'admission of AYair thereto to form-Aa combustible Amixture. Ignitionm-eans 'Il includes a'relatively long vertical'po tion whoseflower end is providedwitha resistance coil 24 electrically connected by conductors A`I9 to a 4source of electrical energy not shown. Conduit I-providingasource ofvfuel for matite desirable to' tiene the resistance zfi by the nare stese.

n 'wuiescauy be deseable to :provide felongated 'Vertice-i fflaiejstack 'for a 'catalytic crack-V ing u'nit 'about 3Go A#feetabove V'ground elevation.V Such a st a'csz sei-'ving a unitprocessing about scooo terrors of resa stook per "day @may be "approxim'ately 24 inches in diameter. The pilot burner 'may v'be constructed of '2-inch `pipe and suitablyl finay be "served witha `fuel 'line about =1` inch Iin."diameter'. "It -tffiii be desirable tofconstruct the Vpilot 'burner tout of `steel `alloy conby weight V"chrostructeci of suitable .electrical *conducting fmate- Y riale. fitshouia b'e'prnno'edof sunicierruyiugged construction-towithstandtemperatures i`4 abbot 2ooo F. 'mausi/'ef :am-0ucso%1niek12ane 20% chromium 'gives satisfactory essere. similar-1y,

Similarly,Y the ignition Videla satisfactory service up to about 2000 F. and may be constructed of close wound 80-20 nickel chromium alloy wound on a 1A; inch arbor for 3A of an inch and then stretched to 11/2 inches. The transformer and the electrical con-- ducting means should be provided to produce a heating current of 60 amperes through the coil at approximately 6.5 volts. v

In order to illustrate the apparatus of the present invention, a small unit was-constructed consisting of 2 inch pipe having a vertical length of l0 feet. A inch tube was run up the side of the 2 inch pipe at the top open end through which gas was passed. A resistance element was placed in the lower end of the 2 inch pipe and, while gas was being introduced into the 2 inch pipe, current was passed through the resistance causing ignition of the combustible mixture of gas and air introduced thereto. The flame travelled upwardly through the 2 inch pipe to the top end thereof and ignited the gas discharging through the inch tubing adjacent thereto. -The-ignition element including a resistance coil ofthe type described in the apparatus of the present invention was subjected to 7() amperes current at '7.5 volts for a period of 5 minutes with no apparent deteriorating eifects. Ordinarily, in igniting the apparatus in accord-- ance with the present invention, it will not be necessary to cause energization of the resistance coil for more than a few minutes at a time.

While specic dimensions and constructional materials have been given 'in describing the improved apparatus of the present invention, it will be apparent to the skilled worker that other dimensions and other construtcional materials may be employed. For example, the burner and the ignition means have been described as being constructed of chromium-nickel alloys and steel. Obviously, other constructional material capable of withstanding the conditions to which the apparatus is put may be used. Likewise, the specific dimensions of the burner mechanism and the ignition means are not critical and may be modied such as by reducing the length oi either the burner conduit or the ignition conduit. For example, the ignition means has been de scribed as having an overall length of about 1G feet. This may be reduced to 3 feet and the gas and air introduced at the bottom thereof and ignited. Once the gas mixture is ignited the current may be cut off and the gas pressure increased forcing the flame above the element and making the short unit serve as a continuous'pilot light in addition to acting as the igniter. In fact, the modification in which the ignition means serves as a burner may be preferred in some instances and, under these circumstances, the burner I4 shown in the several figures of the drawing would be eliminated and the ignition means I would serve as both the burner and the ignition means. Thus, for example, a mixture of gas and air would be ignited in the ignition means Il, the gas being introduced through the conduit i8 and air through ports 26 forming a combustible mixture which would then be passed in contact with the resistance coil 2li which, on energization through electrical conducting means I9 and switch 2l connecting to a source of electrical energy, would cause the combustible fuel-air mixture to be ignited. The current would then be cut off by opening the switch 2l and at the same time the gas pressure would be increased forcing the flame to travel upwardly through the passageway deiined by ignition means il' and outwardly adjacent the open end of elongated stack il. It will thus be seen that one aspect of our invention includes in combination an elongated conduit and an ignition means which serves both as a burner and an ignition means.

1n operating the modification in which the ignition means serves as a burner, the pressure in the ignition means adjacent the region where extension 21 debouches into the ignition means il will be practically atmospheric pressure.V Gas may be supplied through the conduit i8 at a pressure anywhere slightly above atmospheric, for example, 15 pounds per square inch gauge up to about 200 pounds per square inch gauge, which is released nearly instantaneously to slightly above atmospheric pressure as it iiows into the ignitionmeans l1. The element 24 is energized as the mixture rof fuel gas and air passes over it causing ignition and combustion thereof, and after ignitionhas taken place the pressure is increased by about l to 5 pounds per square inch gauge which causes the name to travel up the passageway dened by the ignition means il' and to cause ignition of the combustible fluid being released through stack l i. Ordinarily, the resistance element 24 will bev energized for at least 25 seconds and maybe energized as long as two minutes 'to allow the element to -reach a temperature inthe `neighborhood of 2000 F. to cause ignition of the combustible mixture flowing past the element. The time required for the ignited mixture to reach the open end of the passageway defined by the ignition means l1 from the point of ignition will usually be one second or less.

Thus, in accordance with this mode of our invention, the ignition means serves as the burner and the combustible fuel-air mixture is ignited by energizing the resistance element 24 for a time sufcient to cause ignition and combustion of the combustible mixture. The explosion proof switch 2l is then opened cutting oif the flow of current to the resistance element 24. Gas pressure is then increased slightly by about 1 to 5 pounds per square inch gauge causing the flame to travel up the passageway and ignite the combustible iiuid issuing from stack Il. Numerous modifications will suggest themselves to the skilled workman.

The nature and objects of the present invention having been fully described and illustrated, What we wish to claim as new and useful and to secure by Letters Patent is:

1. A device adapted for the combustion of combustible mixtures which comprises a vertical elongated conduit dening a passageway in iiuid communication at a lower end with a source of ccmbustible fluid and open at an upper end, an elongated vertical burner attached to said elongated conduit adjacent an upper end thereof provided With an interiorly arranged vertical jet and defining a plurality of ports below the jet communicating an interior of the burner with an outer surface thereof, a conduit defining a passageway connected to and communicating said jet with a source of fuel, a vertical ignition means including a resistance element attached to said burner and to said elongated conduit and arranged adjacent said burner and said elongated conduit, said ignition means being provided with a vertical jet and defining a plurality of ports below the jet communicating an interior of the ignition means with an outer surface thereof and being provided with electrical conduction means connecting said resistance element to a source of electrical energy, said burner and said ignition means dening open passageways adjacent the open upper end of the elongatedconduit parallel to each other and to said elongated conduit, and a horizontal bailie member having a plane horizontal surface spaced above and facing the burner and the ignition means, said baille member extending completely over the burner and ignition means and attached thereto and being spaced Vhorizontally from the open end of said elongated conduit whereby said baffle member covers the open end of said burner and ignition means but not the open end of said elongated conduit.

2. A device adapted for the combustion of combustible mixtures which comprises, in vcombina-- tion, a flare stack dening a passageway in fluid communication with a source of combustible uid'at its lower end and open at its upper end, an elongated vertical burner located'on said flare stack adjacent the open upper end provided with -an interiorly arranged vertical iet `and ldeiining a plurality of ports below said jet communicating an interior of the burner with an outer surface thereof, a relatively small conduit defining a passajgeway connecting said jet to a source of fuel, said burner having an open upper end adjacent the open end of said are stack, a vertical ignition means including la resistance element and comprising a conduit located adjacent said burner and said nare stackprovided with an in- -teriorly arranged vertical jet and deiining a plurality of ports below the jet communicating an interior of the ignition means with an outer surface thereof, electrical 4'conducting means con- 8. necting said resistance element to a source of elec-- trical energy, said burner and said ignition means defining open end passageways adjacent said open upper end of said flare stack parallel to each other and to said nare stack, and a horizontal baffle member having a plane horizontal surface spaced above and facing the burner and the ignition means, said baille member extending completely over the burner and ignition means and attached thereto and being spaced horizontally from the open end of said flare stack whereby said baiiie member covers the open end of said burner and ignition means but not the open end of said flare stack.

OLIVER L. CLEVENGER.

WILLIAM A. MCELHANNON.

WILLIAM W. JONES.

References Cited in the le '0f this patent UNITED STATES PATENTS Number Name Date 791,002 Busey May 30, 1905 1,101,789 Doherty June 30, 1914 1,144,784 Rector J une 29, 1915 2,212,875 Camp Aug. 27, 1940 2,276,015 Brodbeck et al Mar. 10, 1942 2,434,627 Schickler Jan. 13, 1948 2,460,016 Kuhn Jan. 25, 1949 2,480,230 Elster Aug. 30, 1949 FOREIGN PATENTS Number Country Date 679,702 Germany Aug. 14, 1939

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