US3379375A - Ignition burner - Google Patents

Description

April 23, 1968 E. S. WALKLING ETAL IGNITION BURNER Filed July 26, 1965 l 2 Sheets-Sheet 1 M ME N702} Ernesi S. Walklmg Edwin C. McKenzie John S. Maskell r Arrow/e A ril 23, 1968 E. s. WALKLING ETAL 3,379,375

IGNITION BURNER Filed July 26. 1965 v 2 Sheets-Sheet 2 United States Patent 3,379,375 IGNITION BURNER Ernest S. Walkling, Orpington, Edwin C. McKenzie, Wallington, and John Maskell, Petts Wood, England, assignors to Babcock & Wilcox, Limited, London, England, a corporation of Great Britain Filed July 26, 1965, Ser. No. 474,578 Claims priority, application Great Britain, July 28, 1964, 29,957/ 64 7 Claims. (Cl. 239-110) ABSTRACT OF THE DISCLOSURE A liquid fuel burner system with provisions for the withdrawal of all residual fuel after the burner is shutdown. The invention includes four separate arrangements, one operating on the principle of suction created by an air ejector, two using the principle of suction created by a piston and one employing positive pressure of steam introduced into the fuel oil conduit at the burner barrel. The system is particularly well suited for systems which burn heavy fuel oil and are used only intermittently such as for lighting-up of main burners. The withdrawn fuel is passed through a separator and discharged into a storage zone remote from the burner system.

This invention relates to liquid fuel burners and more particularly to liquid fuel burners subjected to intermittent use, such as liquid fuel burners for lighting-up main burners of a vapor generating and superheating installation. Following lighting-up of a main burner the associated lighting-up burner is retracted into a housing.

It is desirable that the lighting-up burner should be available for a number of lighting-up operations without requiring removal from the installation for emptying and cleaning between the operations in order to maintain the burner free from blockages arising, for example, from carbonization of residual liquid fuel at the burner head by heat emanating from the main burners or partial solidification of the liquid fuel in the burner barrel or burner feed pipe during long intervals between lighting-up operations.

The use of a heavy fuel oil, such as a fuel oil having a viscosity of 1000 Redwood No. 1 seconds or more, increases the likelihood of the occurrence of blockages.

In a known arrangement of lighting-up burner liquid fuel is circulated continuously through the burner barrel and feed pipe when the burner is not in operation, a shutolf valve being provided at the burner head to prevent discharge of the fuel through the burner head. However, if the shut-off valve becomes partially ineffective through wear or deposition of carbon, leakage of the liquid fuel past the shut-off valve into the housing :may occur with substantial risk of a fire arising in the housing.

In another known arrangement of lighting-up burner, provision is made for purging the burner head with steam or air prior to retraction of the lighting-up burner into the housing. However, during the purging operation the burner head is exposed to the heat output of the main burners which is liable to produce a rapid rise in the temperature of the burner head and accelerate carbonization of any liquid fuel drops remaining in or on the burner head.

According to the present invention, a liquid fuel burner includes a burner head mounted on a burner barrel arranger to be fed with liquid fuel from a main pipe line through a burner fuel pipe, wherein means are provided which are adapted to evacuate liquid fuel from the burner barrel and burner feed pipe through a drain 3,379,375 Patented Apr. 23, 1968 connection following closing of a valve between the burner feed pipe and the main pipe line.

By removing the liquid fuel from the burner valve and feed pipe, deposition of carbon in or on the burner head is eliminated or greatly reduced and blockages due to solidification of fuel in the burner barrel and feed pipe are avoided.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIGURE 1 is a partly diagrammatic sectional side elevation of an ejector pump and separator indicating an associated burner together with feed and drain connections;

FIGURE 2 is a diagrammatic representation of a suction pump and an associated burner together with feed and drain connections;

FIGURE 3 is a diagrammatic representation of a suction cylinder and an associated burner together with feed and drain connections; and

FIGURE 4 is a diagrammatic representation of a burner together with associated feed and drain connections and an auxiliary connection to the burner.

Referring to FIGURE 1, an oil burner 2 is of the steam atomizing type and is connected at a tail piece 4 to a source of supply of oil (not shown) through a main pipe line 5 and a burner feed pipe line 6 and with a source of supply of steam (not shown) through a line 8 provided with a shut-off valve 9. The oil and steam flow in separate streams through a barrel 10, mix in an atomizing head 12 and are discharged from the head as a diverging spray of fine liquid particles.

Positioned in the oil supply line 6 is a shut-off valve 14 and a T-junction 16 having a branch line 18 connected to an ejector pump 20 at an inlet 21.

The ejector pump 20 includes a hollow body 22 within which is located a throat piece 23 having a central convergent-divergent passage 24 and held in position with a hollow nut 25. An injection nozzle tube 26 is slidably mounted in a necked portion 27 of the body 22 and is sealed to the body 22 with an O-ring seal 28. A piston 29 is secured to the upper end of the nozzle tube 26 by means of a bolt 39 threaded into a tapped portion of an axial bore 31 in the nozzle tube. The piston 29 is movable within a cylinder 32 in the body 22 and is sealed to the wall thereof with an O-ring seal 32A. An inlet 33 to the base of the cylinder is connected by a line 34 having a shut-oif valve 35 to a source of supply of air (not shown). The piston is urged towards the base of the cylinder by a spring 36 housed within a cap nut 37 threaded into the end of the body 22. The strength of the spring 36 is such that when air is supplied to the cylinder 32 at a suitable pressure, the piston is moved to the raised position shown. Radial bores 38 are provided through the nozzle tube to connect, when the piston 29 is in the raised position shown, the axial bore 31 in the nozzle tube with the interior of the cylinder.

The lower portion of the nozzle tube 26 includes a shoulder 39 which seats on the body 22 (as shown) to limit upward movement of the nozzle tube, and a tapering nozzle 40 which is arranged to discharge air into a throat portion 41 of the convergent-divergent passage 24 when the nozzle 40 is in an operative position in which the shoulder 39 seats on the body 22. Upon the supply of air at superatmospheric pressure to the cylinder 32 being discontinued, the spring 36 moves the piston 29 downwardly to an inoperative position in which the nozzle 40 seats on the wall 42 of the inlet to the convergenbdivergent passage 24 to close the flow path through the passage between the inlet 21 and an outlet 43 from the body 22.

The outlet 43 from the body is connected by a short line 44 to an inlet 45 to a separator 46 including a casing 47 provided with upper and lower end caps 48, 49. The lower end cap 49 is connected to an oil drain line 50 and the upper end cap 48 is provided with a tubular air vent 51 extending within the casing to a level below the level of the inlet 45.

In operation, the liquid fuel burner is positioned in the wall of a vapor generating and vapor heating installation (not shown) and serves to ignite fuel discharged from an associated main burner. When the oil burner 2 is being fired, the air shut-off valve is closed, and since no air is supplied to the cylinder 32, the spring 36 holds the piston 29 in the inoperative position with the nozzle seating on the wall 42 of the convergent-divergent passage 24 thereby preventing the flow of oil through the branch line 18. Following ignition of the fuel discharged from the main burner, the supply of oil and steam to the lighting-up burner 2 is discontinued by closing the shutoff valves 14 and 9 and the burner is retracted into a housing. The air shut-off valve 35 is then opened and a stream of air at superatmospheric pressure is supplied to the cylinder 32, thereby forcing the piston 29 upwardly and moving the nozzle 40 to the operative position. Air supplied to the cylinder 32 passes through the radial bores 38 to the axial bore 31 and is discharged through the nozzle 40 to the throat portion 41 of the convergent-divergent passage 24 to lower the pressure therein, The reduction in pressure induces a flow of oil from the burner barrel 10 and oil line 6 through the branch line 18 and a mixture of oil and air is discharged to the separator 46 from which the oil passes to the oil drain line 50 and the air passes to the vent 51.

When substantially all of the liquid fuel has been removed from the burner barrel 10 and the lines 6 and 18 the air shut-off valve 35 is closed and the nozzle 40 returns to the inoperative position under the influence of the spring 36 acting on the piston 29.

It will be appreciated that, when a stream of air is supplied to the injector nozzle, care must be taken that an explosive emulsion of liquid fuel and air is not produced.

It will also be appreciated that steam may be supplied through the line 34 instead of air, thereby avoiding the possible generation of an explosive emulsion of liquid fuel and air.

Conveniently, the valves 9, 14 and 35 may 'be actuated in unison, using a single source of actuating fluid, such as the air or steam supplied to the line 34.

In the arrangement shown in FIGURE 2, a suction pump includes a suction chamber 61 formed by a cylinder 62 and a piston 63 movable within the cylinder by a hydraulic, pneumatic or electric motor (not shown).

The chamber 61 is connected to the branch line 18 through a non-return valve 64 such that, following retraction of the burner 2, the piston 63 is operated a number of times by the motor, moving oil from the burner barrel 10 and the lines 6 and 18 during the suction strokes and discharging the oil to the separator 46 on the return strokes through a further non-return valve 65 until substantially the whole of the oil has been evacuated from the burner barrel 10 and the lines 6 and 18.

Alternatively, in another arrangement (not shown) the suction chamber 61 formed by the cylinder 62 and piston 63 is of a volume greater than the volume of the burner barrel 10 and the lines 6 and 18 such that but a single stroke is necessary to remove substantially the whole of the oil from the burner barrel 10 and the lines 6 and 18 following retraction of the burner 2, a return stroke either being made when the burner is put into operation again, returning the oil to the burner barrel or, preferably, being made immediately following the suction stroke while the oil is still warm, discharging the oil to the separator 46, to avoid the necessity of providing a heater for the suction chamber if a heavy oil is used. The piston may be actuated by an actuating piston or by a solenoid and spring return. Alternatively, the chamber 61 may be of a lesser 4 volume and the piston may uncover a suitable drain port at the end of the suction stroke to allow the liquid fuel to flow, by a siphonic action, to the separator.

In the arrangement shown in FIGURE 3, a suction cylinder 70 includes a closed cylinder 71 having a first chamber 72 connected to the branch line 18 through a two-way valve 73 alternatively connecting the first chamber 72 to the drain line 44. The first chamber 71 is separated by a piston 74 from a second chamber 75 connected to the line 6 through a two-way valve 76 which alternately connects the second chamber 75 to the drain line 44. A spring 77 biases the piston 74 away from the end of the cylinder connected to the branch line 18 and is compressible by pressure exerted by the oil in the second chamber 75 acting on the piston 74, The spring 77 is effective, upon release of the pressure exerted by the oil in the second chamber 75, to move the piston away from the end connected to the branch line 18 to induce drainage of substantially the whole of the oil in the burner barrel 10 and the lines 6 and 18 through the branch line 18 into the first chamber.

Thus, when the burner is in the operative position, the valve 73 in the branch line 18 connects the first chamber 72 to the drain line 44 and the pressure of the oil in the line 6 and second chamber 75 acts upon the piston 74 to move the piston towards the end of the cylinder connected to the branch line 18, thus compressing the spring 77. Upon retracting the burner 2 the valve 73 is operated to connect the first chamber to the branch line 18, the valve 14 is closed and the two-way valve 76 isolating the second chamber 75 from the line 6 and connecting the second chamber to the line 44 is operated, thereby releasing the pressure in the second chamber. The piston 74 then moves away from the end connected to the branch line 18 under the action of the spring 77 to reduce the pressure in the first chamber 72 and thereby include drainage of the oil in the burner barrel 10 and the lines 6 and 18 into the first chamber 72. On returning the burner 2 to the operative position the valve 73 is operated to connect the first chamber 72 to the drain line 44, the valve 14 is operated to permit the flow of oil into the line 6 and the valve 76 is operated to permit the flow of oil into the second chamber 75 and isolate the second chamber from drain line 44. The pressure of the oil acting on the piston in the second chamber 75 compresses the spring 77 and urges the oil in the first chamber through the valve 73 to the drain line 44. To facilitate this return stroke, it is necessary, when heavy fuel, oil is being used, to heat the oil in the first chamber. Alternatively, on the conclusion of the initial stroke, under the influence of the spring 77, the first chamber 72 may be connected, through the two-way valve 73, or through a further valve (not shown), to the drain line 44. If connection of the first chamber 72 with the drain line 44 is effected through the further valve, the connections may be arranged such that the draining may be assisted by a siphonic action.

Preferably the three valves 14, 73, 76 are linked together and are operated by the movement of the burner barrel during retraction from or advancement into the furnace chamber.

In the arrangement shown in FIGURE 4, the source of steam at superatmospheric pressure is connected into the burner barrel through a duct 80 formed integral with the barrel at an aperture 81 slightly behind the burner head 12 such that, upon introduction of the steam into the burner barrel, oil between the aperture 81 and the burner head is expelled through the burner head in an equal, or in an approximately equal, period of time as taken by the simultaneous expulsion of oil from between the aperture 81 and the T-junction 16 through the branch line .18.

Thus following retraction of the burner 2, the valve 14 is closed, a valve 82 in the branch line 18 is opened and a valve 83 is opened in a supply line 84 connecting the source of steam at superatmospheric pressure with the duct 36. The steam forces the oil forwardly through the burner head 12 and rearwardly through the line 6 and since the resistance to flow in the path through the burner head 12 is much greater than the resistance to flow in the path through the line 6, the major quantity of the oil will pass through the branch line 18. The supply of steam is discontinued upon substantially all of the oil having been forced from the burner barrel 1i) and tie lines 6 and 13.

What is claimed is:

1. In combination, a fuel burner including an elongated burner barrel, a burner head connected to said burner barrel, a liquid fuel supply line connected to said burner barrel, a fuel valve in said fuel supply line, and means for withdrawing liquid fuel from said burner barrel and said liquid fuel supply line downstream of said fuel valve when said fuel burner is shut down, said withdrawing means including a fuel drain line connected at one end to said fuel supply line between said fuel valve and said burner barrel and at the other end to a storage zone separate from said withdrawing means, whereby substantially all of said withdrawn liquid is removed to said storage zone prior to re-use of said fuel burner, a separating means connected in said drain line between said withdrawing means and said storage Zone for separating the withdrawn liquid fuel from any expansible fluid mixed therethrough, said separating means being separate from said withdrawing means and said storage zone and said liquid fuel supply line.

2. The combination of claim 1 wherein means are provided for introducing pressurized elastic fluid into said burner barrel at a location intermediate its length.

3. The combination of claim 1 wherein said means for withdrawing liquid fuel includes a suction device connected with said fuel drain line.

4. The combination of claim 3 wherein the suction device includes an ejector pump connected to a source of actuating fluid, said ejector pump including a body, means forming a convergent-divergent passage in said body, said passage being in communication With said fuel drain line, and a nozzle arranged to discharge said actuating fluid into the throat of said passage.

5. The combination of claim 4 wherein said nozzle is connected to a spring biased piston, and means are provided for selectively moving said piston and nozzle between an operative and an inoperative position.

6. The combination of claim 3 wherein said suction device includes means forming a suction chamber formed within a cylinder, and a piston movable within said cylinder.

7. The combination of claim 6 wherein said suction chamber is of greater volume than the combined volumes of the burner barrel and the portion of the liquid supply line downstream of the fuel valve.

References tlited UNITED STATES PATENTS 1,516,871 11/1924 Stout l5836 2,397,986 4/1946 Senninger 15836 2,685,919 8/1954 Plass et a1. 158-36 2,686,562 8/1954 MacCracken et al. 15836 2,741,301 4/1956 Lines 158-436 2,818,110 12/1957 Rulseh 15 3-36 2,878,839 3/1959 Gilbert 15S-35 FREDERICK KETTERER, Primary Examiner.

ROBERT A. DUA, Examiner.

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