Closed flare stack with optimized combustion

Abstract

The present invention relates to a closed flare stack (1) comprising a drum (2) having a first upstream inlet (21) associated with a first oxidizer supply (41) and a downstream flue gas outlet, a combustion chamber (3) disposed inside said drum (2) downstream of said first inlet (21) and defining a column (31) between said drum (2) and said combustion chamber (3), said combustion chamber (3) being provided with a second upstream inlet associated with a second fuel gas supply (42). Said flare stack (1) includes an ignition source (5) disposed in said combustion chamber (3) downstream of said second inlet and a first set of diffusers disposed in said combustion chamber (3), upstream of said ignition source (5) and configured to create turbulence between said fuel gas and said oxidizer before their combustion.

Description

technical field

[0001] The present invention relates to the field of industrial flares.

[0002] The present invention relates more particularly to the field of closed flares, also called thermal oxidizers, hidden flame flares, or even non-visible flame flares.

[0003] A closed flare is defined here as a flare configured for gas burning, in which combustion occurs entirely within the flare itself, rather than in the open air. A closed flare is thus distinguished from an open-flame flare, in which combustion typically occurs at the top of the flare.

[0004] The present invention relates in particular to a closed flare whose design promotes complete combustion of gases, so as to minimize the release of polluting compounds, while maintaining a compact design.

[0005] The present invention will thus find many advantageous applications in the petrochemical, chemical, refining, natural gas and energy industries, as well as for onboard flares of cruise ships and / or LNG carriers. Previous art

[0006] The flare industry plays a vital role in gas and hydrocarbon processing, enabling the safe combustion of exhaust gases. Flares are used to burn off residual gases produced during production, maintenance, and safety operations in industrial facilities. They prevent dangerous accumulations of flammable gases and minimize the risk of explosions and fires. Furthermore, flares are often used as a backup solution in case of failure of gas treatment equipment. However, industrial flares are also a significant source of greenhouse gas emissions and air pollution. Therefore, evolving environmental standards and the ongoing pursuit of energy efficiency have necessitated the development of new, more efficient flares.

[0007] From a technical standpoint, current flare designs are quite bulky, which can pose constraints in terms of installation and integration at industrial sites or onboard vessels such as LNG carriers. Furthermore, flares are primarily custom-made. This personalized design therefore presents both a technical challenge and an economic cost. It is thus essential to find solutions that streamline and simplify the flare design and manufacturing process, thereby reducing costs while maintaining high levels of quality and performance.

[0008] Another major technical challenge is to improve combustion emissions to comply with the regulations for Classified Installations for Environmental Protection (ICPE). The design of flares must therefore be optimized to accommodate high flow rates while ensuring optimal combustion performance, thereby meeting greenhouse gas emission standards and contributing to environmental protection.

[0009] Such emissions depend on the proper execution of combustion. In particular, incomplete combustion in the flare stack results in the formation of incomplete combustion products such as carbon monoxide (CO), unburned hydrocarbons, or volatile organic compounds (VOCs), which contribute to air pollution. Incomplete combustion generally produces a yellow flame, while complete combustion produces a blue flame.

[0010] Combustion reactions are generally incomplete. One known solution is to supply an excess of oxidant at high temperature, particularly a large excess of oxygen, which reduces emissions of incomplete combustion products but promotes the formation of nitrogen oxides (NOx). Achieving complete combustion and minimizing polluting compounds is therefore complex.

[0011] To improve combustion, it is known to implement a star-shaped or toroidal gas inlet in the flare stack, which distributes the gas diffusion to allow for better mixing between the gas and air. However, such shapes are complex and difficult to manufacture. Furthermore, these shapes are not suitable for high gas flow rates. In particular, with toroidal gas inlets, increasing the flow rate would require either adding more tori or enlarging their diameter, thus increasing the overall size.

[0012] Document CA3065353 describes a flare stack equipped with a cross burner, consisting of multiple tubes extending around a central section. The tubes have orifices at their downstream end, aligned with the direction of gas flow, i.e., in their upper portion. The gas is thus injected at various points within the airflow rather than at a single point. However, the gas-air mixture remains limited and, as stated above, difficult to adapt to high gas flow rates.

[0013] Other solutions also aim to facilitate the mixing of gas and air. Document US20060166152 describes a flare stack whose combustion chamber is equipped with a burner, a pilot downstream of the burner that creates a flame, and a diaphragm upstream of the burner that redirects the air towards the flame. This solution thus only affects the air, attempting to maximize the air delivered directly to the burner and the pilot, thereby limiting the amount of gas that can be delivered and generating turbulence only for the air, without affecting the fuel gas.

[0014] Document WO2006010693 discloses a flare stack in which air and gas are fed to a fan, which discharges a mixture of air and gas. A Venturi effect is implemented downstream of the fan, creating a laminar flow without turbulent movement. Furthermore, the homogeneity of the mixture produced by the fan is not guaranteed.

[0015] Other solutions integrate the flare stack into a flare gas capture and utilization system, also known as FUCU, in which the flare stack's output is routed to engines or turbines to generate electricity, or used as fuel in industrial processes. Such implementation is highly dependent on the industrial sector and the availability of suitable infrastructure.

[0016] The Applicant therefore submits that there is currently no satisfactory alternative flare solution that allows for complete gas combustion while maintaining a simple design adaptable to a wide range of flow rates. Summary of the invention

[0017] The present invention aims to improve the current situation described above.

[0018] The present invention aims more particularly to remedy the above disadvantages by proposing a flare whose internal structure is adapted to promote combustion, while minimizing constraints on the gas supply.

[0019] To this end, the object of the present invention relates, in a first aspect, to a closed flare stack for the combustion of combustible gas, the flare stack comprising: a drum having a first upstream oxidizer inlet and a downstream flue gas outlet; a combustion chamber disposed inside the drum downstream of the first inlet, the combustion chamber extending along a portion of the length of the drum and delimiting a column between the drum and the combustion chamber, the combustion chamber being open upstream and downstream and having a second upstream fuel gas inlet; a first oxidizer supply associated with the first inlet; at least a second fuel gas supply associated with the second inlet; at least one ignition source disposed in the combustion chamber downstream of the second inlet; and a first set of diffusers disposed in the combustion chamber, upstream of the ignition source and configured to create turbulence between the fuel gas and the oxidizer before their combustion.

[0020] As stated above, the flare stack according to the present invention is a closed flare stack. The flare stack is configured so that combustion takes place entirely within the drum, preferably within the combustion chamber. It is also understood that the upstream and downstream openings of the combustion chamber allow fluid circulation between the drum and the combustion chamber. The drum defines, in particular, the shape and external structure of the flare stack.

[0021] For example, a drum approximately 6 meters high is planned, which primarily houses the other components along its lower section, up to a height of 2 meters, to facilitate access. The combustion chamber, for instance, is 1 meter high and is positioned 1 meter above the drum. In particular, the flare stack extends mainly vertically, with the drum and combustion chamber thus extending vertically.

[0022] Furthermore, the concepts of upstream and downstream will be understood in relation to the direction of gas and flue gas flow within the flare stack. The oxidizer enters the flare stack through the first inlet, via the first feed, and the fuel gas enters through the second inlet, via the second feed. The oxidizer and fuel gas flow through the flare stack towards the downstream outlet. The oxidizer partially enters the combustion chamber and mixes with the fuel gas. Specifically, the upstream and downstream openings of the combustion chamber preferably correspond to its longitudinal ends. The mixed gases ignite at the ignition source, producing hot flue gases. Since the ignition source is located within the combustion chamber, combustion occurs primarily, and preferably entirely, within the combustion chamber.

[0023] A portion of the oxidizer also circulates, from upstream to downstream, in the column, around the combustion chamber. This portion corresponds to cold oxidizer, not involved in the combustion reaction. At the outlet of the combustion chamber, the cold oxidizer and the hot flue gases mix, forming cold flue gases, that is, flue gases with a temperature lower than the hot flue gases. The cold flue gases continue circulating until they reach the downstream outlet of the flare stack.

[0024] The downstream outlet is advantageously located at the top of the flare stack, so that the gas circulation corresponds to a circulation from the bottom to the top of the flare stack, naturally corresponding to the circulation of hot gases.

[0025] The oxidizer could be air, for example, and the upstream inlet could be a simple opening in the flare stack to the outside air. The fuel gas could be VOCs, methane, or more generally any polluting gas whose compounds can be at least partially transformed by combustion into other compounds, preferably less toxic or polluting. The reaction products generated during combustion naturally depend on the oxidizer and fuel used, but are primarily carbon dioxide and water.

[0026] The gas supply system upstream of the flare stack includes, for example, a set of safety and / or measuring devices to ensure that the fuel gas is supplied in a controlled manner. This might include, for instance, a pressure gauge to measure the incoming gas pressure, a flow meter to measure or read the gas flow rate, a throttling valve and a second pressure gauge to regulate the fuel pressure supplied to the flare stack, as well as a flame arrestor to prevent any flame propagation in the gas network upstream of the flare stack. These measuring instruments allow for adjustments to the amount of oxidizer in parallel with the fuel gas supply, or to other variables such as the flame temperature.

[0027] The ignition source can be, for example, a spark plug, a pilot light creating a flame, or electrodes generating an electric arc. In the field of flares on ships, the ignition source is generally electrodes.

[0028] Those skilled in the art understand that a single combustion chamber can accommodate multiple gas supplies and multiple ignition sources. Each gas supply, for example, is paired with an ignition source to form a burner, with the combustion chamber housing multiple burners, perhaps arranged adjacent to one another. Diffusers can be integrated into the combustion chamber and control multiple burners, or they can be specifically assigned to each burner, i.e., to each gas supply. It is also understood that using multiple burners allows the same burner design to be applied to a variety of flare stack sizes, without requiring changes to the burner itself.

[0029] The flare stack, for example, is connected to a control cabinet that allows for its operation, i.e., the control of the power supply (flow rate and / or pressure) and the ignition source. Depending on the design, a control cabinet can be configured for manual operation, or a programmable logic controller (PLC) can be configured for automated control of the flare stack.

[0030] For the purposes of this invention, a diffuser is defined herein and throughout the following description as a component that interferes with the flow of fluid in the flare stack, particularly oxidizer, combustible gas, or flue gases. Those skilled in the art will understand that, in thermodynamics, a diffuser is a device that controls fluid flow by reducing its velocity and increasing its static pressure. The diffuser also allows for the distribution of fluids, that is, the creation of turbulence within a space, for example, in the combustion chamber. Diffusers may consist, for example, of sheet metal plates or fins that at least partially impede the flow of fluid, thereby altering its circulation.

[0031] It is understood here that the first set of diffusers promotes mixing between the oxidizer and the fuel gas by generating turbulence in the upstream-downstream circulation. Such turbulence corresponds to a movement of the oxidizer and / or fuel gas distinct from the natural upstream-downstream circulation. The diffusers are thus arranged in the combustion chamber, where the mixing takes place, upstream of the ignition source. The first set of diffusers can, in particular, be positioned at least partially upstream of the second inlet, so as to direct the oxidizer in a way that promotes mixing with the fuel gas. The first set of diffusers can also be positioned at least partially downstream of the second inlet, so as to redirect the oxidizer and fuel gas to generate turbulence.

[0032] The Applicant submits that the turbulence generated by the diffusers allows for mixing of the oxidizer and the fuel gas, which promotes complete combustion. Indeed, since combustion is a reaction between the oxidizer and the fuel gas, a good mixture of the compounds ensures that the reactants are sufficiently supplied to sustain the reaction and consume all the fuel gas. As stated above, incomplete combustion can result in the formation of incomplete combustion products that contribute to air pollution.

[0033] Here, the turbulence generated by the diffusers results in turbulent combustion, in which the fuel gas and oxidizer are intensively mixed. This makes combustion more efficient and improves fuel utilization. Furthermore, because the diffusers are positioned upstream of the ignition source, mixing is at least partially achieved before combustion, ensuring that it begins under optimal conditions.

[0034] Thanks to the present invention, it is therefore possible to obtain stable, uniform combustion with fewer polluting emissions, namely greenhouse gases, fine particles, and nitrogen oxides. More complete combustion also allows for a reduction in flame size within the combustion chamber. The flare according to the present invention thus enables efficient combustion and accommodates a wide variety of gas flow rates without significant constraints on the gas supply. Furthermore, the cooling of the flue gases through the propagation of fresh air along the inner wall of the drum also results in a cooler drum wall, allowing the use of materials such as common stainless steel (e.g., 304 or 316), which is much lighter than the bricks and refractory fiber mats traditionally used, less toxic, easier to maintain, and easily dismantled.

[0035] In an advantageous embodiment of the present invention, the first set of diffusers is configured to create opposing fluid movements towards a central portion of the chamber and towards a peripheral portion of the chamber.

[0036] Those skilled in the art understand that opposing movements create high shear in the fluids, which promotes mixing. For example, the oxidizer is directed from the periphery to the center of the combustion chamber, and the fuel gas is directed from the center to the periphery. Consequently, the oxidizer and fuel gas collide, generating shear and mixing. This design ensures that the resulting turbulence leads to fluid mixing and optimized combustion. In particular, creating opposing movements is far more efficient than simply rotating the gases within the combustion chamber, which would result in low shear and poor fluid mixing.

[0037] In an additional embodiment, the first set of diffusers includes first diffusers arranged along a peripheral portion of the chamber and oriented obliquely towards a central portion of the chamber.

[0038] It is understood here that the first diffusers are configured to redirect the fluid from the peripheral portion to the central portion of the combustion chamber. For example, the first diffusers are arranged to redirect the oxidizer after its separation between the combustion chamber and the column. The portion of the oxidizer entering the combustion chamber is then disturbed by the first diffusers and redirected to the central portion, towards the fuel gas.

[0039] In addition, the first diffusers make it possible to increase the velocity of the oxidant by locally reducing the cross-section of the combustion chamber.

[0040] The first diffusers, for example, are assembled with the combustion chamber wall. It is also understood that the oblique orientation of the first diffusers corresponds to a progressive reduction in the cross-section of the combustion chamber, from upstream to downstream. In other words, the first diffusers are fixed on one side to the combustion chamber wall, and extend downstream and into the interior of the combustion chamber on the other.

[0041] In an embodiment that can be combined with the previous one, the first set of diffusers includes second diffusers, arranged along a central portion of the chamber and oriented obliquely towards a peripheral portion of the chamber.

[0042] In other words, the second diffusers extend together, from a central section, downstream and towards the periphery of the combustion chamber. The fluid coming into contact with the second diffusers thus separates towards the walls of the combustion chamber.

[0043] The combination of the first and second diffusers creates a first fluid movement, from the periphery towards the interior of the combustion chamber, and a second fluid movement, from the interior towards the periphery of the combustion chamber. These two opposing movements result in significant turbulence and shear, ensuring the mixing of fluids before and during combustion.

[0044] Preferably, the first diffusers are placed upstream of the second diffusers.

[0045] This design is particularly advantageous when the first diffusers are configured to redirect the oxidizer towards the interior of the combustion chamber, and the second diffusers are configured to redirect the fuel gas towards the periphery of the combustion chamber. The first diffusers can be positioned upstream, downstream, or at approximately the same height as the second feed without conflicting. Specifically, with the first diffusers positioned at approximately the same height as the second feed, and the second diffusers positioned downstream of the second feed, the oxidizer is redirected towards the fuel gas as it collides with the second diffusers, thus maximizing turbulence.

[0046] It is understood here that a person skilled in the art can adjust the respective arrangement of the diffusers to maximize turbulence and fluid mixing. The Applicant submits, however, that placing the first diffusers slightly upstream of the second diffusers provides better mixing and combustion.

[0047] In yet another embodiment, the second supply is arranged along the central portion, upstream of the second diffusers.

[0048] It is understood here that the central arrangement of the second feed promotes the interaction of the fuel gas with the second diffusers, so as to ensure that the fuel gas is carried along in a turbulent motion.

[0049] Preferably, the second feed is placed in the vicinity of the second diffusers, so that the gas comes into direct contact with and is redirected by the second diffusers.

[0050] Thus, the fuel gas is supplied to the central section by the second feed and redirected to the peripheral section, whereas the oxidizer splits between the combustion chamber and the column and is redirected to the central section. Mixing between the fuel gas and the oxidizer is therefore facilitated without requiring a complex fuel gas supply design.

[0051] By combining the previous means, we thus obtain a design in which the oxidant is redirected from the peripheral portion to the central portion, and the fuel gas is redirected from the central portion to the peripheral portion, creating a mixing zone and turbulence between the two fluids.

[0052] In one specific embodiment, the second diffusers have a V shape.

[0053] Preferably, the V-shape is oriented to direct the fluid towards the peripheral portion. In other words, the second diffusers extend both downstream and towards the periphery of the combustion chamber, and the V-shape gradually widens downstream. The fluid coming into contact with the second diffusers thus separates towards two opposite walls of the combustion chamber.

[0054] It is understood here that the V-shape allows for the creation of fluid movement towards the walls of the combustion chamber, while maintaining a simple design. For example, a square combustion chamber is envisioned, with the first diffusers arranged along two opposite walls of the combustion chamber and the second diffusers oriented towards these same walls, corresponding to a very simple embodiment of the invention. In another design, the second diffusers have a conical shape, the V-shape corresponding to a cross-section of the second diffusers. The combustion chamber advantageously has a circular cross-section, with the first diffusers arranged along the inner perimeter of the combustion chamber.

[0055] Preferably, the second diffusers are oriented so that the V shape has an angle between 90° and 130°.

[0056] Preferably, the V shape has an angle between 100° and 120°.

[0057] Preferably, the V shape has an angle of approximately 110°.

[0058] Here we understand that the V shape consists of two branches, extending on either side towards the walls of the combustion chamber, the angle of the V shape corresponding to the angle between the branches.

[0059] It is also understood that the angle between the arms corresponds to the orientation of the second diffusers, and therefore to their impact on fluid movement, particularly the movement of the fuel gas. The angle thus affects turbulence and combustion to a greater or lesser extent. The Applicant submits here that an angle of 110° provides the best results and minimizes the flame size in the combustion chamber compared to other angles, indicating more complete combustion.

[0060] In one embodiment, the second diffusers have a plurality of notches formed along their ends.

[0061] In other words, the second diffusers are equipped with a plurality of orifices, in particular orifices opening onto three faces of the second diffusers. For example, a plurality of regularly spaced orifices are provided so that the second diffusers have a "comb" shape.

[0062] The Applicant submits that providing a plurality of notches along the second diffusers creates alternating flows promoting the formation of turbulence and mixing between fluids, further facilitating complete combustion and reducing the flame height.

[0063] Optionally, the first diffusers are also expected to have openings, for example notches like the second diffusers or openings of other shapes.

[0064] In another embodiment, the first set of diffusers includes third diffusers arranged along a central portion of the chamber and oriented transversely to the upstream-downstream direction of circulation in the chamber.

[0065] The third diffusers, for example, are oriented almost perpendicularly to the upstream-downstream direction. In other words, in a flare extending mainly vertically, the third diffusers are arranged almost horizontally.

[0066] Preferably, the third diffusers define an intermediate space between them, through which fluids can flow. Advantageously, third diffusers are provided in the form of two flat elements, for example, two flat sheets separated by a central groove. In a circular design, it is also possible to use a flat element with a central orifice forming the intermediate space.

[0067] Third diffusers are distinguished in particular from a sieve or other perforated structure as described below, in that the fluid cannot flow through the third diffusers and must bypass them.

[0068] Those skilled in the art understand that the third diffusers create a "dead zone" downstream where the oxidizer and fuel gas mix. The mixing of fluids in the dead zone also corresponds to opposing movements towards the central and peripheral portions of the chamber. The fluids can indeed flow downstream of the third diffusers via the peripheral portion, around the third diffusers, before moving towards the dead zone, i.e., towards the central portion; or they can flow downstream via the central portion, in the space between the third diffusers, before moving towards the dead zone, i.e., towards the peripheral portion.

[0069] The Applicant further submits that the use of third diffusers generates as much turbulence as a combination of first and second diffusers. It is therefore possible to implement a simple design comprising only third diffusers, without first or second diffusers, requiring less material. In particular, their central position allows them to be easily attached to the second feed, without requiring mounting on the combustion chamber walls, unlike first diffusers. Third diffusers attached to the second feed are easier to remove, along with the feed, for maintenance operations, unlike first diffusers attached to the combustion chamber.

[0070] Compared to the second diffusers, the third diffusers can also be arranged similarly, although they are subjected to less intense temperatures. This is because the angled shape of the second diffusers results in higher temperatures at their ends. The third diffusers are thus subjected to lower temperatures and heat gradients, increasing their durability.

[0071] Of course, it remains possible to design a system combining third diffusers with other diffusers. For example, it is possible to design a combustion chamber with multiple burners, each associated with a different diffuser, or to position the third diffusers downstream or upstream of the first and / or second diffusers. However, such a combination does not appear necessary to achieve sufficient turbulence while maintaining a simple design.

[0072] Preferably, the second supply is arranged along the central portion, upstream of the third diffusers.

[0073] The third diffusers, for example, as previously stated, are attached directly to the second feed, for instance via spacer plates. Similarly, a second feed located near the third diffusers ensures that the fuel gas is directly drawn into turbulent motion to promote mixing.

[0074] Thus, by combining the previous embodiments, the second supply is arranged along the central portion, upstream respectively of the second diffusers or the third diffusers.

[0075] In a specific embodiment, the first feed and the second feed are sized to form a first mass dilution ratio in the drum of between 90 and 130, between the oxidizer and the fuel gas.

[0076] Preferably, the first mass dilution ratio is about 110.

[0077] Here, the mass dilution ratio refers to the ratio between the mass of oxidizer and the mass of fuel gas. In other words, for one dose (by mass) of fuel gas in the drum, between 90 and 130, preferably 110, doses (by mass) of oxidizer are required.

[0078] The mass dilution ratio allows control of the temperature at the flare stack outlet, with a higher ratio corresponding to a lower temperature. The Applicant submits that a ratio of approximately 110 results in an outlet temperature of approximately 425°C after the mixing of cold and hot flue gases. It is understood that the mass dilution ratio can be adjusted according to the target flare stack outlet temperature. In particular, the aim here is to obtain a stack outlet temperature that is lower than the auto-ignition temperature of the combustible gas, specifically methane.

[0079] It is further understood that the mass dilution ratio depends directly on the supply of oxidant and combustible gas in the drum, and therefore on the respective sizing of the first and second feeds, as well as the pressure losses in the drum resulting from friction against the various elements, in particular the pressure losses generated by the diffusers.

[0080] In another embodiment that can be combined with the previous embodiment, the first feed, the second feed, the barrel and the combustion chamber are sized to form a second mass dilution ratio, in the combustion chamber, of between 30 and 50.

[0081] Preferably, the second mass dilution ratio is about 40.

[0082] It is understood here that the second mass dilution ratio corresponds to the respective proportions of oxidizer and fuel gas, specifically within the combustion chamber. Since the fuel gas is directly fed into the combustion chamber, and the oxidizer is split between the combustion chamber and the column, the second ratio depends on both the fluid supply and the dimensions of the drum and combustion chamber, in order to control the distribution of the oxidizer within the combustion chamber and the column. The diffusers also generate, depending on their shape, a Venturi effect that can impact the first and / or the second mass dilution ratio.

[0083] In combination with the previous embodiment, a first ratio of between 90 and 130 is obtained and a second ratio of between 30 and 50, with for example between 60 and 80 doses (by mass) of oxidizer in the column for one dose (by mass) of combustible gas in the flare, the column being devoid of combustible gas but allowing the subsequent cooling of the hot fumes.

[0084] As before, the second mass dilution ratio allows for temperature control within the combustion chamber. The target combustion temperature is between 1000°C and 1100°C, for example, approximately 1040°C. In particular, an insufficiently high temperature would result in incomplete combustion, while an excessively high temperature presents safety risks and puts stress on the flare stack itself. Generally, in a closed flare stack, those skilled in the art aim for a combustion temperature of at least 800°C.

[0085] It is also understood that the temperatures in the flare stack must be determined in conjunction with the materials used. For example: a drum resistant to a temperature of up to 800°C, for example made of 304L stainless steel, the drum being exposed to cold fumes; a combustion chamber and a second feed (in the combustion chamber) resistant to a temperature of up to 1100°C, for example made of a refractory material such as 310S stainless steel.

[0086] In one embodiment, the second feed comprises a tube extending transversely through the combustion chamber, the tube being provided with orifices along its downstream portion.

[0087] It is understood here that the tube extends transversely with respect to the flare stack, that is to say, perpendicular to its longest dimension. In other words, and taking as a reference a flare stack extending vertically, the tube extends in a substantially horizontal manner, perpendicular to the height of the flare stack, and perpendicular to the upstream-downstream direction.

[0088] It is also understood that the downstream portion of the tube is determined in relation to the upstream-downstream direction of flow within the flare stack, specifically directly from the downstream outlet. In a flare stack extending vertically, with the outlet located at the top of the stack, the downstream portion of the tube corresponds to its upper section.

[0089] The orifices thus correspond to the gas inlet into the combustion chamber. It is understood that small orifices, relative to the tube's size, increase the velocity of the fuel gas entering the combustion chamber and contacting the diffusers, thereby increasing turbulence. The orifices might be, for example, oblong holes drilled along the length of the tube in the transverse direction. In another example, the orifices might be a row of circular orifices. In particular, small orifices allow the gas to be expelled like a nozzle, propelling it at high speed both along the central axis of the orifices and to the sides, thus maximizing turbulence.

[0090] Preferably, the orifices are positioned opposite the diffusers, so that the combustible gas is directed towards the diffusers.

[0091] It is understood here that this design allows the combustible gas to be projected, at high velocity, towards the diffusers, for example the second diffusers described above, in order to redirect the combustible gas and generate turbulence.

[0092] According to one variant, the orifices are arranged at a distance from the downstream end, for example distributed in two sections located at an angle to the downstream end, so that the combustible gas is oriented obliquely with respect to the upstream-downstream direction. The two sections are, for example, arranged at approximately 45° to the downstream end, and at approximately 90° to each other.

[0093] It is understood that a combustible gas projected obliquely into the combustion chamber maintains a downstream velocity, while generating turbulence during its movement. Conversely, a gas oriented in the opposite direction to the upstream-downstream direction will lose velocity during mixing and be redirected downstream.

[0094] In a specific embodiment, the flare includes a sieve disposed in the combustion chamber upstream of the ignition source and downstream of the first set of diffusers, the sieve forming a flame arrester delimiting the combustion chamber into a first premixing zone and a second combustion zone.

[0095] It is clear here that the screen serves both to delimit the combustion chamber, preventing a flashback upstream of the second zone, and to slow the upstream-downstream flow of gases in the first zone. The provision of a screen therefore promotes premixing of the oxidizer and the combustible gas before they pass through it.

[0096] In yet another embodiment, the flare stack further includes a second set of diffusers, arranged in the barrel, downstream of the combustion chamber, and configured to mix the hot fumes from the combustion chamber with the cold oxidizer from the column.

[0097] It is understood here that, like the first set of diffusers, the second set of diffusers creates turbulence that promotes mixing. The Applicant submits, in particular, that without the second set of diffusers, a portion of the cold oxidizer remains at the periphery of the drum, and the hot fumes from the combustion chamber are only partially cooled. The provision of the second set of diffusers thus improves the cooling of the hot fumes, resulting in homogeneous, cool fumes.

[0098] In one embodiment, the first power supply includes a fan provided in the upstream portion of the drum, the fan being configured to generate a flow in the drum.

[0099] For example, an axial fan is planned, which can be mounted directly inside the drum. An axial fan generates a low static pressure, which is sufficient considering the pressure losses in the drum. At the combustion chamber, the flow in the drum splits into a first flow in the combustion chamber and a second flow in the column, which rejoin after the combustion chamber. For example, the first feed, the combustion chamber, and the drum are sized to obtain a flow rate of 3000 m³ / h inside the combustion chamber and 5000 m³ / h inside the column (i.e., a total flow rate of 8000 m³ / h generated by the fan).

[0100] The oxidizer supply is managed, for example, by controlling the fan. A thermocouple configured to measure the flame temperature and a UV scanner configured to monitor the presence of the flame are advantageously used, with the fan being controlled based on the thermocouple readings.

[0101] The fan can also be controlled based on one or more of the measuring instruments described above. In particular, controlling the fan based on a measurement of the fuel gas pressure (via a pressure gauge) and / or a measurement of the fuel gas flow rate (via a flow meter) provides faster and more efficient regulation than using a thermocouple.

[0102] According to other variations, the flare stack corresponds to an air-draft flare stack, meaning that the primary air supply is essentially a simple opening. An air-draft flare stack thus has no fan or is equipped exclusively with an auxiliary fan, used solely for safety reasons, for example, to reduce the temperature in case of a runaway reaction.

[0103] The Applicant further submits that the use of a fan makes it possible to ensure a higher speed in the drum than by drawing air, while generating static pressure, which guarantees the formation of turbulence in the desired area.

[0104] Thus, through the various functional and structural technical characteristics described above, the Applicant proposes a closed flare stack configured to facilitate the mixing of oxidizer and fuel, promoting complete combustion without constraints on the fuel gas supply. The manufacture and design of flare stacks is thereby greatly simplified by guaranteeing high performance for a variety of flow rates, without requiring custom design for each application. Description of the figures

[0105] The features and advantages of the present invention will become apparent from the description of the specific and non-limiting examples of embodiments of the present invention below, with reference to figures 1 to 8 attached and on which: [ Fig.1 ] There figure 1 illustrates a perspective view of a closed torch according to an embodiment of the present invention; [ Fig. 2 ] There figure 2illustrates a cross-sectional view of a torch conforming to the figure 1 ; Fig.3 ] There figure 3 illustrates a detailed view of a cross-section conforming to the figure 2 , according to a first example of implementation; [ Fig. 4 ] There figure 4 schematically illustrates a cross-sectional view of a combustion chamber conforming to the figure 3 ; Fig. 5 ] There figure 5 schematically illustrates a cross-sectional view of another example of a combustion chamber conforming to the figure 3 , the combustion chamber being equipped with a sieve; Fig. 6 ] There figure 6 schematically illustrates a detailed view of a cross-section of a torch conforming to the figure 1 , according to a second example of implementation; [ Fig. 7 ] There figure 7 schematically illustrates a cross-sectional view of a combustion chamber conforming to the figure 6 ; Fig. 8 ] There figure 8schematically illustrates a cross-sectional view of another example of a combustion chamber conforming to the figure 6 the combustion chamber being equipped with a sieve. Detailed description

[0106] A closed flare with optimized combustion will now be described in what follows, with joint reference to figures 1 to 8 The same elements are identified with the same reference symbols throughout the description that follows.

[0107] As stated in the description's preamble, flares must be designed to ensure the most complete combustion possible in order to minimize their emissions. Current solutions for promoting this complete combustion involve integrating toroidal or star-shaped gas feeds, which are complex in design and have limited flow rates.

[0108] One of the objectives of the present invention is to propose a flare allowing more complete combustion of gases, while maintaining a simple design suitable for a wide range of flow rates.

[0109] This is made possible in the example described below.

[0110] As illustrated in the figures 1 to 8 The example described here includes a closed flare stack 1 configured for the combustion of combustible gas. The combustible gas could be, for example, VOCs, methane, carbon dioxide, etc., or a mixture of these gases. Flare stack 1 is specifically sized for the combustion of methane. Flare stack 1 may be integrated into a larger system for capturing and utilizing flare gas, or, in another example, it may be a flare stack on a ship.

[0111] The flare stack 1 comprises a shaft 2, which defines its external structure and is equipped with a first upstream inlet 21 and a downstream outlet 22, so that the gases flow from upstream to downstream. Preferably, the shaft 2 extends vertically, with the first inlet 21 located in the lower portion and the outlet 22 in the upper portion for vertical gas flow, from bottom to top. In particular, the first inlet 21 corresponds to an oxidizer inlet and is associated with a first oxidizer supply 41. The oxidizer corresponds, for example, to air. The shaft 2 extends, for example, to a height of approximately 6 m, with the majority of the flare stack 1 components located in the lower portion of the shaft 2, up to a height of 2 m to ensure easy access.

[0112] Advantageously, and as illustrated in the figures 2 And 3The first feed 41 includes a fan in the upstream portion of the drum 2, i.e., in this case, the lower portion. The fan is configured to generate a flow within the drum 2, from upstream to downstream. Advantageously, the fan is an axial fan, whose axis extends along the height of the drum 2, generating a high flow rate and low pressure along the axis for upstream-downstream circulation.

[0113] According to other variations, flare 1 corresponds to an air-draft flare, meaning that flare 1 is simply open upstream, its operation naturally generating a flow from upstream to downstream without requiring a fan. To facilitate air intake, the drum 2 rests on a set of feet, allowing air circulation beneath the drum 2 at the level of the first inlet 21. It would also be possible to design a drum 2 resting on a base with open side walls for air intake, the fan then being positioned downstream of the openings.

[0114] Furthermore, when the oxidant corresponds to a fluid other than outside air, the first supply 41 corresponds for example to a dedicated circuit, for example an oxygen supply circuit.

[0115] Inside barrel 2, and as illustrated in the figures 2 to 8A combustion chamber 3 is provided. The combustion chamber 3 extends along a portion of the length of the drum 2, for example, approximately 1 m long, downstream of the first inlet 21. Furthermore, the combustion chamber 3 is open upstream and downstream, i.e., here at the top and bottom, so as to communicate with the interior of the drum 2. The combustion chamber 3 also defines a column 31 between the drum 2 and the combustion chamber 3; that is, the cross-section of the combustion chamber 3 is smaller than that of the drum 2, so as to leave a space between the combustion chamber 3 and the drum 2. Thus, the oxidant circulating in the drum 2 separates between the column 31 and the interior of the combustion chamber 3, and the oxidant circulating in the column 31 rejoins, downstream, the fluid from the combustion chamber 3.

[0116] As illustrated in the figures 3 And 6The combustion chamber 3 is advantageously fixed to the inner wall of the drum 2 via mounting brackets 35, which allow for the assembly and support of the combustion chamber 3 and associated components. The mounting brackets 35 are preferably inclined at an angle of approximately 45° to improve the stability of the combustion chamber 3 and to maximize the distance of heat transfer, by conduction through the mounting brackets 35, between the combustion chamber 3 and the drum 2. The inclination of the mounting brackets 35 thus reduces the risk of thermal bridging compared to a more horizontal fixing. This inclination also facilitates assembly / disassembly operations on the combustion chamber by increasing the clearance around the components.However, those skilled in the art understand that such an inclination reduces the mechanical strength of the fastener, and that increasing the thickness of the mounting brackets 35 to compensate for this lack of strength would increase heat conduction. The design of the mounting brackets 35 is therefore aimed at achieving a balance, providing sufficient mechanical strength to support the combustion chamber 3 under all operating conditions, while minimizing heat conduction.

[0117] In accordance with the figures 1 to 8 , the combustion chamber 3 is equipped with a second upstream inlet 32 ​​( figure 1 ), associated with a second 42 combustible gas supply.

[0118] Outside the flare stack 1, the second supply 42 can be equipped with a set of safety and / or measuring devices to provide a controlled supply of fuel gas. These devices include a first pressure gauge 43 to measure the inlet gas pressure, a flow meter 44 to measure the gas flow rate, a throttling valve 45 to regulate the fuel pressure, and a second pressure gauge 46 to check the outlet pressure of the throttling valve 45, as well as a flame arrestor 47 to prevent any flame propagation in the gas network. Alternatively, a variant is possible in which the first supply 41 is designed similarly to provide a controlled and secure supply of oxidizer.

[0119] Inside the flare stack 1, the second feed 42 advantageously comprises a tube extending transversely through the combustion chamber 3, that is, here in a substantially horizontal manner. The tube is provided with a plurality of orifices 49 along its downstream portion, that is, here in its upper portion. As illustrated in the figure 3 The 49 openings here correspond to oblong holes, depending on the length of the tube. In the figure 6 The orifices 49 correspond to circular holes arranged along the tube. The fuel gas is thus drawn into the interior of the combustion chamber 3 and projected at high speed through the orifices 49. In particular, the small size of the orifices 49 compared to the cross-section of the tube increases the speed of the fuel gas, thereby increasing turbulence as described below. Furthermore, the fuel gas is ejected, like a nozzle, in multiple directions from the orifices 49.

[0120] The combustion chamber 3 is thus supplied with both oxidizer and fuel gas. Downstream of the second inlet 32, an ignition source 5 is provided, configured to initiate combustion between the oxidizer and the fuel gas. The ignition source 5 could be, for example, a spark plug, a pilot light creating a flame, electrodes generating an electric arc, or any other means known to those skilled in the art for starting the reaction between the oxidizer and the fuel gas. As illustrated in the figures 2 , 3 And 6The ignition source 5 extends from the inside of the combustion chamber 3 to the outside of the flare stack 1, notably to allow for its control. For example, a control cabinet 48 is provided, configured to control the first power supply 41, i.e., the fan speed, and / or the second power supply 42, for example, the actuation of the throttling valve 45, and / or the ignition source 5, for example, the generation of a spark, a flame, an electric arc, etc. In another variant, the flare stack 1 is connected to a programmable logic controller (PLC) configured for automated control of the above elements.

[0121] Thus, through the action of the ignition source 5, combustion is initiated in the combustion chamber 3, causing the oxidizer and the fuel gas to react and generating hot flue gases. These hot flue gases continue the upstream-downstream circulation of the fluids and mix with the oxidizer from the column 31 to form cold flue gases, which leave the flare 1 through the outlet 22, here at the top of the flare 1. In an advantageous variant, means are provided to promote the mixing of the hot and cold flue gases, so as to obtain a homogeneous mixture of cold flue gases, for example a second set of diffusers arranged in the drum 2, in particular fixed to the walls of the drum 2 and extending obliquely, so as to redirect the cold oxidizer towards the hot flue gases and force mixing.

[0122] Specifically, the ratio of oxidizer to fuel gas can be controlled to regulate the temperature of the cold flue gases exiting the drum 2, i.e., the average temperature, corresponding to the temperature of perfectly mixed cold flue gases. This ratio is directly derived from the sizing of the first feed 41 and the second feed 42, namely the respective flow rates of feeds 41 and 42, as well as the pressure losses generated by circulation in the drum 2, particularly due to the diffusers 6 described below. A first mass dilution ratio between 90 and 130 is advantageously used, corresponding to the weight of oxidizer from the first feed 41 relative to the weight of fuel gas from the second feed 42.In particular, a first ratio of approximately 110 is preferred, resulting in an outlet temperature of around 425°C when the fuel gas is methane, which is below the auto-ignition temperature of methane. This design ensures that the emissions will not ignite, even if residual fuel gas is present.

[0123] More generally, it can be predicted that the first mass dilution ratio is determined so that the temperature at outlet 22 is lower than the auto-ignition temperature of the combustible gas.

[0124] Similarly, the ratio between oxidizer and fuel gas inside the combustion chamber 3 can be controlled to regulate the temperature of the hot flue gases, and more generally the temperature inside the combustion chamber 3. This ratio is derived both from the sizing of the first feed 41 and the second feed 42 as above, as well as from the sizing of the drum 2 and the combustion chamber 3, which determine the distribution of the oxidizer between the column 31 and the combustion chamber 3. A second mass dilution ratio of between 30 and 50 is therefore advantageously provided in the combustion chamber 3. In particular, a second mass dilution ratio of approximately 40 is preferred, allowing a temperature in the combustion chamber 3 to be between 1000°C and 1100°C.

[0125] More generally, the second mass dilution ratio is determined so that the temperature in the combustion chamber 3 allows for efficient and safe combustion. In particular, the temperature in the combustion chamber 3 must be lower than a maximum temperature associated with the materials used in the combustion chamber 3. For example, a drum 2 made of 304L stainless steel, which withstands temperatures up to 800°C, and a combustion chamber 3 and a second feed 42 made of 310S stainless steel, a refractory material resistant up to 1100°C, are used.

[0126] In particular, the combination of the first mass dilution ratio and the second mass dilution ratio makes it possible to achieve a distribution of the oxidant of 30% to 40% in the combustion chamber 3 for 60% to 70% in the column 31.

[0127] In the example of the figure 3In addition, viewing windows 8 are provided to allow visualization of the interior of the drum 2 and the combustion chamber 3, particularly to verify that combustion is proceeding as desired. Obviously, such viewing windows 8 are not essential to the operation of the flare stack 1 itself. Visualizing the interior of the combustion chamber 3 allows, for example, differentiation between a diffusion flame and a premix flame, and therefore determination of whether the oxidizer and the fuel gas are mixed at the correct concentrations.

[0128] In accordance with the concept of the invention, and to ensure that combustion takes place optimally, the flare 1 is equipped with a first set of diffusers 6 ( figures 3 to 8 ) upstream of the ignition source 5. The first set of diffusers 6 opposes the upstream-downstream flow of the oxidizer and the fuel gas in order to create turbulence between the two gases, before their combustion.

[0129] In the example of figures 3 to 5 The first set of diffusers 6 thus comprises first diffusers 61, arranged along a peripheral portion of the combustion chamber 3, and oriented obliquely towards a central portion of the combustion chamber 3. Here, the first diffusers 61 are thus fixed to an internal wall of the combustion chamber 3 and extend towards the center of the combustion chamber 3. Any fluid circulating in the combustion chamber 3, in particular the oxidizer from the barrel 2, is then redirected from the periphery towards the center of the combustion chamber 3. The fluid velocity is simultaneously increased, the first diffusers 61 locally reducing the cross-section of the combustion chamber 3.

[0130] In conjunction, the first set of diffusers 6 also includes second diffusers 62 arranged along the central portion and oriented obliquely towards the peripheral portion. The second diffusers 62 thus mirror the first diffusers 61 and redirect the fluids from the center to the periphery of the combustion chamber 3. In particular, the second diffusers 62 can be arranged so as to redirect the combustion gas, from the second feed 42, towards the periphery of the combustion chamber 3. The second diffusers 62 advantageously have a V-shape, that is to say, a shape that gradually widens downstream on either side of the center of the combustion chamber 3. The V-shape has, for example, an angle α between 90° and 130°, between 100° and 120°, and most preferably about 110° in order to optimize the movement from the center to the periphery of the combustion chamber 3.

[0131] The first set of diffusers 6 is thus configured to create opposing fluid movements, on the one hand towards a central portion of the combustion chamber 3, and on the other hand towards a peripheral portion of the combustion chamber 3. In particular, the first diffusers 61 are oriented towards the central portion of the combustion chamber 3 which receives the second diffusers 62, and the second diffusers 62 are oriented towards the peripheral walls of the combustion chamber 3 which receive the first diffusers 61. The opposing fluid movements thus create a strong shear between the different flows, which promotes the mixing of the oxidizer and the fuel gas.

[0132] In another example illustrated by the figures 6 to 8The first set of diffusers 6 comprises third diffusers 65 arranged along the central portion and oriented transversely to the upstream-downstream direction. In other words, the third diffusers 65 extend substantially horizontally between the central and peripheral portions. Advantageously, the third diffusers 65 are in the form of two flat plates separated by an intermediate space, allowing fluid circulation between the two plates. In the example described here, the plates are between 600 mm and 1000 mm long and 50 mm wide, separated by a space of 25 mm. The length of the plates can be adjusted according to the power of the flare stack 1. As illustrated in the figure 7The third diffusers 65 are thus bypassed by the fluids along the central and peripheral portions, creating a dead zone downstream which "draws" the fluids from the central portion to the peripheral portion and vice versa. This behavior then generates significant turbulence.

[0133] Thus, the first set of diffusers 6 allows for a mixture of the oxidizer and the fuel gas, particularly before ignition by the ignition source 5. This mixture promotes complete combustion of the fuel gas by ensuring a sufficient supply of oxidizer at every point in the combustion chamber 3, where combustion takes place. More complete combustion therefore reduces the residual amount of fuel gas in the flue gases exiting the flare stack 1, as well as minimizing the presence of incomplete combustion products, such as carbon monoxide, VOCs, nitrogen oxides, fine particles, etc.

[0134] Of course, the design of flare stack 1 can still be optimized to promote turbulence and ensure complete combustion. In the example of the figures 3 to 5It is thus anticipated that the first diffusers 61 are positioned upstream of the second diffusers 62. Furthermore, the first diffusers 61 are positioned approximately at the same level as the second feed 42, and the second diffusers 62 are positioned slightly downstream of the second feed 42, which is located in the central portion of the combustion chamber 3. The upstream positioning of the first diffusers 61 promotes the redirection of the oxidizer towards the center of the combustion chamber 3, and the downstream positioning of the second diffusers 62 promotes the redirection of the fuel gas towards the periphery of the combustion chamber 3. In the example of the figures 6 to 8 The second feed 42 is also placed in the central portion of the combustion chamber 42, the third diffusers 65 being placed slightly downstream of the second feed 42, substantially in the same position as the second diffusers 62 of the figures 3 to 5 .

[0135] In the example of figures 3 and 4 The orifices 49 are positioned directly opposite the diffusers 6, specifically opposite the second diffusers 62. The orifices 49 are arranged along the downstream end of the tube, that is, its upper end. The fuel gas is thus projected, through the orifices 49, against the diffusers 6 to promote its redirection and the generation of turbulence.

[0136] In another example illustrated by the figure 5The orifices 49 are arranged so that the fuel gas is oriented obliquely, i.e., the gas is introduced directly into the combustion chamber 3 in such a way as to create turbulent motion. The orifices 49 are, for example, oriented approximately 45° to the upstream-downstream direction, i.e., here to the vertical, so that the fuel gas moves downstream while generating turbulence, in conjunction with the turbulent motion of the oxidizer. Depending on the exact design of the combustion chamber 3, it is also possible to arrange the orifices 49 so that the fuel gas is oriented obliquely and towards the diffusers 6, for example, towards the first diffusers 61, or towards the third diffusers 65 as illustrated in the figure 8 Conversely, and as illustrated in the figures 6 And 7, the orifices 49 can also be arranged according to the downstream end of the tube, so that the combustible gas is directed between the third diffusers 65.

[0137] Furthermore, it is also possible to incorporate notches 63, 64 on the diffusers 6 to create additional fluid flows that stimulate mixing. In the example of the figure 3 , we thus provide for first notches 64 made on the first diffusers 61, as well as second notches 63, arranged regularly in the shape of a "comb", on the second diffusers 62.

[0138] Finally, according to a specific variant illustrated in the Figures 5 And 8An additional screen 7 is provided in the combustion chamber 3, upstream of the ignition source 5 and downstream of the first set of diffusers 6. The screen 7 advantageously forms a flame arrester, so that the combustion chamber 3 is divided into a first premixing zone 33, in which the fluid is in turbulent motion to mix the fuel gas and the oxidizer, and a second combustion zone 34, to which the reaction is confined. The screen 7 both prevents combustion from flowing back upstream and slows the downstream flow, promoting the mixing of the oxidizer and the fuel gas to ensure complete combustion.

[0139] Thus, it will be understood that the present invention provides for a closed flare stack whose internal structure greatly promotes turbulent movement of the oxidizer and fuel gas. This movement results in turbulent combustion, which allows for comparatively more complete combustion. Furthermore, the use of diffusers to generate turbulence corresponds to a simple design to implement, not limited to specific flow rate ranges, and without constraining the shape of the gas supply.

[0140] It should be noted that this detailed description relates to a particular embodiment of the present invention, but in no way does this description limit the scope of the invention; on the contrary, its purpose is to remove any possible inaccuracy or misinterpretation of the following claims.

[0141] It should also be noted that the reference signs in parentheses in the following claims are in no way intended to be limiting; these signs are solely intended to improve the intelligibility and understanding of the following claims and the scope of the protection sought.

Claims

1. A closed flare stack (1) for the combustion of combustible gas, said flare stack (1) comprising: - a drum (2) having a first upstream oxidizer inlet (21) and a downstream flue gas outlet (22); - a combustion chamber (3) disposed inside said drum (2) downstream of said first inlet (21), said combustion chamber (3) extending along a portion of the length of said drum (2) and defining a column (31) between said drum (2) and said combustion chamber (3), said combustion chamber (3) being open upstream and downstream and having a second upstream combustible gas inlet (32); - a first oxidizer supply (41) associated with said first inlet (21); - at least one second combustible gas supply (42) associated with said second inlet (32); - at least one ignition source (5) disposed in said combustion chamber (3) downstream of said second inlet (32);and - a first set of diffusers (6) arranged in said combustion chamber (3), upstream of said ignition source (5) and configured to create turbulence between said fuel gas and said oxidizer before their combustion, ; characterized in that said first set of diffusers (6) is disposed at least partially downstream of said second inlet (32) so as to redirect said oxidant and said combustible gas for the formation of said turbulence.

2. Torch (1) according to claim 1, wherein said first set of diffusers (6) is configured to create contrary movements of fluid towards a central portion of said chamber (3) and towards a peripheral portion of said chamber (3).

3. Torch (1) according to claim 1 or 2, wherein said first set of diffusers (6) comprises first diffusers (61) arranged along a peripheral portion of said chamber (3) and oriented obliquely towards a central portion of said chamber (3).

4. Torch (1) according to any one of claims 1 to 3, wherein said first set of diffusers (6) comprises second diffusers (62), arranged along a central portion of said chamber (3) and oriented obliquely towards a peripheral portion of said chamber (3).

5. Torch (1) according to claim 4 in combination with claim 3, wherein said first diffusers (61) are arranged upstream of said second diffusers (62).

6. Torch (1) according to any one of claims 4 or 5, wherein said second diffusers (62) have a plurality of notches (63) formed along their ends.

7. Torch (1) according to any one of claims 1 to 3, wherein said first set of diffusers (6) comprises third diffusers (65) arranged along a central portion of said chamber (3) and oriented transversely to the upstream-downstream direction of flow in said chamber (3).

8. Torch according to any one of claims 4 to 7, wherein said second feed (42) is arranged along said central portion, upstream respectively of said second diffusers (62) or of said third diffusers (65).

9. Flare (1) according to any one of claims 1 to 8, wherein said first feed (41) and said second feed (42) are sized to form a first mass dilution ratio in said drum (2) of between 90 and 130, preferably of about 110, between said oxidizer and said fuel gas.

10. Torch (1) according to any one of claims 1 to 9, wherein said first feed (41), said second feed (42), said barrel (2) and said combustion chamber (3) are dimensioned to form a second mass dilution ratio, in said combustion chamber (3), of between 30 and 50, preferably of about 40.

11. Torch (1) according to any one of claims 1 to 10, wherein said second feed (42) comprises a tube extending transversely through said combustion chamber (3), said tube being provided with orifices (49) along its downstream portion.

12. Torch (1) according to claim 11, wherein said orifices (49) are arranged opposite said diffusers (6), so that said combustible gas is directed towards said diffusers (6).

13. Torch (1) according to any one of claims 1 to 12, which includes a screen (7) disposed in said combustion chamber (3) upstream of said ignition source (5) and downstream of said first set of diffusers (6), said screen (7) forming a flame arrester delimiting said combustion chamber (3) into a first premixing zone (33) and a second combustion zone (34).

14. Torch (1) according to any one of claims 1 to 13, which further comprises a second set of diffusers, disposed in said barrel (2), downstream of said combustion chamber (3), and configured to mix the hot fumes from said combustion chamber (3) with the cold oxidizer from said column (31).

15. Torch (1) according to any one of claims 1 to 14, wherein said first feed (41) comprises a fan provided in the upstream portion of said drum (2), said fan being configured to generate a flow in said drum (2).

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