WO2008096061A2

WO2008096061A2 - Burner pilot flame and use thereof

Info

Publication number: WO2008096061A2
Application number: PCT/FR2007/002131
Authority: WO
Inventors: Gérard Mougey; Marc Deux; Frédérick BEAU
Original assignee: Total Raffinage Marketing
Priority date: 2006-12-28
Filing date: 2007-12-20
Publication date: 2008-08-14
Also published as: FR2910955B1; WO2008096061A3; FR2910955A1; WO2008096061A8

Abstract

The invention relates to a pilot flame for the burner of an industrial furnace, comprising an annular chamber for premixing at least one fuel and air at one end, and a flame carrier device (2) at the other end, the two ends being connected by a central hollow portion (3), characterised in that the inner profile of the pre-mixing annular chamber, which is preferably located outside the combustion area of the furnace, is of the convergent type in the direction of the central hollow portion (3) for enabling the required suction of a portion at least of the air necessary for the combustion of the pilot flame, wherein the flame carrier device (2) located inside the furnace combustion chamber in the vicinity of a burner includes an additional air inlet means, in that the flame carrier device (2) includes a flame retaining means that comprises a metallic member heated at a high temperature by the pilot flame, and in that the additional air inlet means is located in the vicinity of the flame retaining means and the upper end of the central hollow portion upstream from them and at a distance of the pre-mixing chamber downstream from it. The invention also relates to the use of such pilot flame.

Description

PILOT LIGHT AND USE THEREOF

The present invention relates to a pilot and its method of use, when it is associated with a burner installed on any type of furnace or boiler, particularly in the field of petroleum refining or petrochemistry.

In an oil refinery, several types of furnaces are used to bring the required temperatures to hydrocarbon feedstocks, upstream of the refinery process steps.

These furnaces, which can adopt a cylindrical or parallelepipedic shape, are generally equipped with several burners whose number may vary from one to several tens for the same furnace, with burner heating power ranging from 500 to more than 5000 therms per hour.

Usually the burners are totally fueled with gas or oil, or by a gas and fuel mixture.

The burners, generally open flame, can be arranged on a sole or on the walls of the oven, at one or more levels. The hydrocarbon feedstock to be heated circulates in a bundle of tubes which extends along the inner wall of the furnace, in the radiation zone, and then in the convection zone located at the upper level of the furnace.

The furnace is an essential and essential element in any industrial process, such as petroleum refining or the petrochemical industry, and a power loss by extinguishing one or more burner (s), or a total cessation of the furnace, irremediably causes a loss of efficiency of downstream processing processes, which leads to a deterioration in the quality of the products manufactured, or even a total cessation of production.

There is therefore a primary interest for the operator that furnaces or boilers installed in different manufacturing processes, operate constantly at their best performance for optimal exploitation.

In addition to this key element, which is the stability and smooth operation of an oven in a petroleum refining process, the safety aspect for people and equipment is also imperative. In fact, a confined accumulation of large quantities of unburned combustible gases by accidental burners extinguished, there is a significant risk of explosion when restarting (igniter flame, hot spots, or electric spark) uncontrolled, can cause destruction of the oven and endangering operating personnel. To avoid the aforementioned problems and mainly those inherent to the safety aspect, burner operators and manufacturers have associated with each of the burners, a device usually referred to as a burner pilot, or a pilot burner. , in order to ensure the presence as close to the burner of a permanent and stable flame which represents a safety element, in order to avoid any accumulation of unburned fuel in the confined enclosure that is an oven.

Thus, manufacturers have proposed pilot lights associated with a type of burner, fed by a separate fuel circuit, preferably gas, with a supply of air located outside the oven, the night lights being generally arranged closer to the burners.

In order for the addition of a pilot light to a burner to provide a safety element with regard to possible unwanted extinguishings of said burner, it is essential that the flame of the pilot light be permanent, whatever the events, for example thermodynamic, external.

Unfortunately, it turns out that several industrial situations, some of which are indicated below, may promote the uncontrolled extinguishment of the flame of a pilot burner of a furnace burner or boiler.

The diameter of the calibrated orifice of the fuel gas nozzle, generally less than 1 mm, combined with a feed gas of industrial quality, that is to say able to convey solid particles of very small dimensions, are two factors may cause the nozzle to clog and thus extinguish the pilot.

The pilot flame is subjected to the operating conditions of the burner, so the oven, it can be blown, that is to say detached (or unhooked) of the flame holder device of the pilot (also called in the profession "nose of the night light"), by a supply of air or more precisely by a speed of displacement of this air too important. This supply of air usually occurs, for an oven operating with a natural air draft, in the event of a change in the flue gas register, thus causing a sudden change in the gradient of the gas depressions inside the furnace. Another source of uncontrolled air supply that can cause the pilot flame to blow may be from the burner fans operating with pulsed air.

The molecular composition of the fuel gas of the local industrial network can be random, with for example hydrogen contents that can vary in large proportions (20 to 100% by volume) thus causing changes in the speed of propagation of the flame, with a risk major stall and therefore extinction of said pilot flame.

Solutions exist today in the art to overcome these types of extinction risks, for example the change of the nose of the night light depending on the composition of the fuel gas, but their effectiveness is not total and, of more, as above indicated, not universal.

The Applicant has thus remedied the disadvantages mentioned above by improvements in the general geometry of the pilot lights in order to have a reliable and constant safety element associated with each furnace burner or boiler. The research of the

Applicant's main object was thus a modification of the air / gas pre-mixing chamber of the pilot, as well as a new profile for the nose of said pilot.

The present invention therefore relates to a night light for an industrial furnace burner having at one of its ends an annular chamber premix of at least one fuel and air, and at the other end a door device flame, the two ends being connected by a hollow central part, characterized in that

the internal profile of the annular premix chamber, preferably located outside the combustion zone of the furnace, is of the convergent type in the direction of the hollow central part to allow the suction required for at least a part the air necessary for the combustion of the pilot flame, the flame-holder device, located inside the combustion zone of the furnace near a burner, comprises a complementary air inlet means, and in that,

said flame-holder device comprises a means for attaching the flame constituted by a metallic element carried at high temperature by the pilot flame, and in that the complementary air inlet means is located near the flame; means of attachment of the flame and the upper end of the hollow central portion, upstream thereof, and away from the premix chamber, downstream of the latter.

Advantageously, the annular chamber premix has a central supply for fuel, comprising a tube terminating in a nozzle whose axis is situated in the axis X ⁷ X of said chamber and a supply means air consisting of lights located on the wall of said chamber, preferably adjustable flow.

The calibrated orifice of the nozzle equipping the pilot, object of the present invention, is arranged perpendicular to the axis of the premix chamber. The diameter of this calibrated orifice is between 1 and 4 mm, preferably between 2 and 3 mm, thus, by its large dimensions, to limit the risk of blockages most common of this type of nozzle. In addition, in order to eliminate as much as possible any possibility of obstruction of the nozzle, filtration of the combustible gas is preferably carried out upstream of the nozzle. The fuel gas supply tube terminating in the nozzle, adopts at said nozzle, an internal profile of the type converge towards the calibrated orifice.

The nozzle being disposed on the axis of the premix chamber and the latter also adopting a convergent type profile towards the hollow central portion which may be, in a preferred version of the present invention, a central hollow tube connecting the two ends of the pilot, said pre-mixing chamber behaves like the upstream part of a nozzle, or a venturi without its diverging part, causing an increase in the speed of the gases that move from the jet to the nozzle. inlet of the hollow tube towards the nose of the pilot. With this increase of the velocity of the gases and in application of the principle of the dynamics of the fluids (Bernoulli equation) is created a depression thus making it possible to suck up the air necessary for the combustion the pilot by means of an air supply means opening into the premix chamber. Preferably, this air supply means comprises means for controlling the flow rate, therefore the air suction, which can be manual or automatic, or remotely controlled in a process of automatic regulation of the combustion conditions of the night lights. for example an oven or a boiler. The supply means may be a movable ring pierced with several lumens, for example three lumens facing the same lumens disposed on the wall of the premix chamber.

The ratio of the largest to the smallest diameter of the annular premix chamber is between 2 and 6 and preferably between 2.5 and 4. The length of said chamber is equal to about 4 to 8 times its smaller diameter, preferably 5 to 7 times. The flow rate of the fuel gas is between 2 and 15 Nm ³ / H and preferably between 3 and 8 Nm ³ / H. The pressure of the fuel gas is regulated between 0.1 and 2 bar and preferably between 0.3 and 0.8 bar.

According to a preferred variant of the invention, the hollow central portion is substantially cylindrical in shape. According to a preferred embodiment, the pilot is substantially longitudinal axis (X'X), but the hollow central portion connecting the two ends can adopt a curvature angle to facilitate the installation of said nightlight in, or at most near a burner.

In order to avoid a detachment of the pilot flame, which may go to extinction, the flame holder device preferably comprises a flame attachment means located at the other end of that supporting the pre-chamber. -mixed. Different types of hung flames can be constituted by any type of metal elements, such as tubes, plates, installed alone or in combination with each other. In a particularly preferred embodiment of the invention, this means consists of a cross formed by two perpendicularly arranged plates crossing in a line substantially parallel to the direction of the flame. It is this brace, placed directly in the flame which, when raised in temperature, constitutes a hot spot or, more exactly, a larger hot surface than the night-light noses. art, hot surface that remains facilitator of the maintenance of the flame at the exit of the nose of the night light.

To improve the stability of the combustion of the air / gas mixture of the night-light and thus to avoid flame-outings of said night-light in case, for example, of significant variations in the molecular composition of the fuel gas, the Applicant has added a means of complementary air intake at the nose of the night light. Preferably, this means, which is an annular orifice allowing a complementary air inlet, is located according to a preferred embodiment of the invention, on the side of an inlet end_dudit flame holder device, in the direction of circulation of the air and fuel mixture, more precisely on the opposite side to that of the flame attachment means. The additional air comes from the supply air of the burners, which may be, depending on the case, the primary air or the secondary air distributed by a register system, the said registers being generally unsealed, or by air present in the furnace combustion chamber, or by the air fans of the burners operating with pulsed air. The internal vacuum of the furnace, determined by the opening of the smoke register, allows suction of this complementary air at the nose of the pilot. Advantageously, baffles, arranged on the complementary air inlet path and downstream of the end of the hollow central part conveying the air / gas mixture, make it possible to ensure mixing and homogenization of the fuel mixture with the complementary air.

The ratio of the surfaces of the complementary air inlet annular orifice on the end of the hollow central portion is between 2 and 4, preferably between 2.5 and 3.5.

Preferably, according to the invention, the flame-holder device comprises at least one hollow cylindrical portion pierced with at least one orifice and partially covering the means for attaching the flame in order to enhance the stability of the combustion of the flame. . The or holes drilled in this cylindrical portion can limit the extent of the flame by a new supply of air at the base of the flame. Preferably, the pilot is made of a refractory stainless steel. The invention also relates to a method of using the pilot as described in the present invention, the method being such that one proceeds to an ignition of the flame:

- either manually by a portable igniter, - or by an electrode connected to a high voltage electrical circuit.

The present invention is explained in more detail with the aid of FIGS. 1 to 5, representing different embodiments and different parts of an embodiment of a pilot of a refinery furnace according to the present invention.

Various embodiments of the invention will be described hereinafter as examples.

In this description, reference is made to the accompanying drawings in which:

Figure 1 is a schematic overview of a nightlight according to the invention.

Figure 2 is a detail view of Figure 1, in particular of the upper end of the pilot according to the invention. Figure 3 is a sectional view of Figure 2.

Figure 4 is a detail view in section of Figure 1, in particular the lower end of the pilot according to the invention.

Figure 5 is a partial sectional view of a detail of Figure 3 along the line W. Figure 1 is a general schematic view of a pilot according to the invention. The burner 1 is substantially longitudinal axis X ⁵ X, and positioned generally parallel to the axis of the burner. It is entirely made of refractory stainless steel of qualities 310 s for the nose and 304 L for the rest of the night light. It comprises, in the lower and lower part, a central feed 4, equipped with a connecting means 17 to a feed tube for the fuel, and an air supply 16 which is formed by openings made in a movable ring 26 , whose different positions allow a flow adjustment. The central feed 4 is described in detail and in section in FIG. 4.

The night light comprises, at the top and at the top, a flame-holder device 2 intended to carry the flame generated by the burning of air and at least one fuel. A hollow central portion 3 connects the central supply portion 4 and the flame holder device 2. The length of the hollow central portion 3 furthermore makes it possible to attenuate any backfires due to unstable air intake. This length is due to the distance of the central feed portion 4, intended to be placed outside the combustion zone of the furnace, and the flame holder device 2, located inside the zone of burning the oven, near a burner.

The hollow central portion 3 is substantially cylindrical about the axis X ⁷ X, but can adopt a bent or curved profile according to the installation requirements in the furnace or boiler. A support device or flat annular plate 5, which may be removable or welded to the hollow central portion 3, is provided for fixing the pilot in a burner (not shown). FIG. 2 is a detail view of FIG. 1, in particular of the upper end comprising the flame holder device 2 of the pilot light according to the invention, FIG. 3 being a sectional view of FIG. 2 and FIG. 5 is a partial sectional view of a detail of FIG. 3. The flame-holder device 2 comprises a cylinder 7 with an X axis X ⁷ pierced with orifices 9, surrounding a base 14 on which are welded, preferably, two plates 10 and 1 1 forming means for attaching the flame, each of these two plates 10 and 1 1 being also welded to the inner part of the cylinder 8. The base 14 is a ring welded to the inner face of the cylinder 8, perpendicularly to the axis X ⁷ X. The two plates 10 and 1 1 are arranged perpendicularly to one another and intersect in a line on the axis X ⁷ X of Figure 2. A representation of the arrangement of these two plates 10 and 11 is shown in fig 5 which is a sectional view along the lines e W of FIG. 3. Air A arrives (see arrows in FIG. 2) through an annular orifice 29 forming a complementary air inlet means and situated on the side of the inlet end of the device carrying flame 2, in the direction of circulation of the air and fuel mixture, more precisely on the opposite side to that of the attachment means of the flame. The nightlight being placed in a chamber (the oven) placed under vacuum by natural draft and the complementary air coming from the outside (burner and its register), the air will be sucked through the orifice annular 29 then will be added and mixed, the premix air / gas arriving through the end 12 of the hollow central portion. This end 12 opens downstream of the annular orifice 29 inside the cylinder 8, in the direction of circulation of the air and fuel mixture. FIGS. 1 to 3 clearly show that the annular orifice 29 forming the complementary air inlet means is located near the flame attachment means and the upper end 12 of the hollow central portion and at a distance of the premix chamber 21 of the central feed portion 4. The additional air inlet means 29 is further located downstream of the premix chamber 21 and upstream of the flame attachment means and the upper end of the hollow central portion, in the fluid flow direction.

Due to this arrangement, this complementary air is exclusively dedicated to the flame stability of the flame holder device.

In addition, as already mentioned, this distance, corresponding to the length of the hollow central portion, mitigates possible backfires. The base 14 in the form of a ring is arranged between the arrival of the air / gas premix (end 12) and the two plates 10 and 11 forming the attachment means of the flame, and behaves like a baffle thus promoting mixing complementary air and air / gas. Specifically, the base 14 in the form of a ring is disposed between the end 12 of the hollow portion and the air inlet openings 9. Those skilled in the art will be able to adapt the dimensions of the crown in order to obtain a better mixing of the different fluids as a function of the burner pressure and flow rates, as well as that of the vacuum of the furnace.

The cylinder 8 is held on the hollow central portion 3 by at least three fin supports 15 welded to it and located at 120 ° to each other with respect to the base of the cylinder 8.

Figure 4 is a detail view in section of Figure 1, in particular the lower part or central feed 4 of the pilot according to the invention. The central feed 4 comprises a means for adjusting the air flow rate associated with the air inlets 16. The fuel arrives via a hollow cylindrical duct 17 forming a means of connection to a supply of said gas, and discharges through a hollow cylindrical pipe 18, cut in a conical portion 19, tip up, and metallic, of the central feed 4, in a nozzle 20. This nozzle 20 is located substantially at the height of the air inlets 16. The feed The central unit 4 also comprises a pre-mixing chamber 21, annular, of axis X ¹ X, whose internal profile converges towards the hollow central portion 3. The air, sucked through the air inlets 16_by the depression created in the chamber 21, is mixed with the fuel leaving the nozzle 20, and arrives by a convergent portion, in the premix chamber 21.

The air and fuel mixture thus created continues its path through a pipe 22 and a pipe 23, these two pipes being cut in the upper part 25 of the central feed 4. The mobile ring 26 formed of a cylindrical part pivoting around the piece 25, along the axis X ¹ X, allows the adjustment of the air flow rate through the orifices 16.

The pilot burner, object of the present invention, adapts to any type of burners for ovens or boilers. In a small footprint, the flame stability is ensured by an optimal performance of the air / gas mixture at the pre-mixing chamber and the combustion nose, thus enabling pulse-free operating regimes to be achieved. retro combustion.

In addition, it has a very high resistance to the stall of the flame, it accepts any type of fuel present in an oil refinery with a wide rangeability of gas pressures, while being adapted to different conditions of furnace draw.

It is by improving its reliability, made possible by its new geometry, that the pilot object of the present invention, when it is associated with a burner installed on an oven or a boiler, makes it possible to increase and improve the safety of people and equipment in the perimeter of heating installations, including all types of products.

Claims

1. Pilot (1) for an industrial furnace burner having at one of its ends an annular chamber (21) for premixing at least one fuel and air, and at the other end a device for flame (2), the two ends being connected by a hollow central portion (3), characterized in that

the internal profile of the pre-mixing annular chamber (21), preferably located outside the furnace combustion zone, is of the convergent type in the direction of the hollow central part (3) so as to allow the suction required for at least a portion of the air necessary for the combustion of the pilot flame,

the flame-holder device (2), located inside the combustion zone of the furnace near a burner, comprises a means (29) of complementary air inlet, and in that, said device carries flame (2) comprises a flame catching means (10, 1 1) consisting of a metallic element carried at high temperature by the pilot flame, and in that the means (29) for entering the flame complementary air is located near the flame attachment means and the upper end (12) of the hollow central portion, upstream thereof, and away from the premix chamber (21) downstream of the latter.

2. pilot (1) according to claim 1, such that the annular chamber (21) premix comprises a central feed (4) for fuel, consisting of a tube (17) ending in a nozzle (20), the axis is located in the axis X'X of said chamber, and an air supply means (16) consisting of slots located on the wall of said chamber, preferably with an adjustable flow rate.

3. pilot (1) according to the preceding claim, such that the nozzle (20) has a calibrated orifice whose diameter is between 1 and 4 mm and preferably between 2 and 3 mm.

4. pilot (1) according to one of the preceding claims, such that the hollow central portion (3) is substantially cylindrical in shape.

5. pilot (1) according to one of claims 1 to 4, such that the hollow central portion (3) is curved or bent.

6. pilot (1) according to one of claims 1 to 4, such that the pilot (1) is substantially longitudinal axis [X ⁷ X).

7. Pilot (1) according to one of the preceding claims, such that it comprises a means (26) for adjusting the air supply means (16) manually or automatically or remotely controlled.

8. pilot (1) according to one of the preceding claims, such that the ratio of the largest diameter to the smallest diameter of the annular chamber 21 is between 2 and 6 and preferably between 2.5 and 4.

9. Pilot (1) according to one of the preceding claims, such that the length of the annular chamber (21) premix is equal to about 4 to 8 times, preferably 5 to 7 times its smallest diameter.

10. Pilot (1) according to one of the preceding claims, such that the additional air inlet means of the flame holder device (2) is an annular orifice (29) located on the side of an inlet end. of said flame holder (2) in the direction of flow of the air / fuel premix.

1 1. pilot (1) according to claim 1, such that the additional air comes from the burner damper.

12. pilot (1) according to one of claims 10 or 1 1, such that baffles are disposed downstream of said end of the hollow central portion of the path of the complementary air inlet.

13. pilot (1) according to one of claims 10 to 12, such that the ratio of the surfaces of the annular orifice (29) of complementary air inlet on said end of the hollow central portion is between 2 and 4 and preferably between 2.5 and 3.5.

14. Pilot (1) according to one of the preceding claims, such that the means (10, 11) of attachment of the flame consists of any type of metal elements such as tubes, plates, alone or in combination.

15. pilot (1) according to claim 14, such that the means (10, 1 1) of attachment of the flame consists of two plates (10, 11) arranged perpendicularly intersecting along a line substantially parallel to the direction of the flame.

16. Pilot lamp (1) according to one of the preceding claims, such that the flame-holder device (2) comprises at least a part cylindrical (8) hollow pierced with at least one orifice (9) and partially covering the means for fastening the flame.

17. Pilot (1) according to one of the preceding claims, such that the material constituting the pilot is a refractory stainless steel.

18. A method of using a pilot according to one of the preceding claims, such that one proceeds to the arrival of fuel and air and ignition of the flame manually or by an electrical device.