Burner system for biomass synthesis gases

Abstract

A system for burning a synthesis gas obtained from biomass thermal treatment, may have: a combustor having a central axis and including a combustion head, the combustion head having: a central flame outlet configured to emit a flame, a first gas outlet extending around the central axis and located radially outwardly of the central flame outlet relative to the central axis and configured to inject a first gas into the combustor along a first direction having an axial component relative to the central axis, and a second gas outlet extending around the central axis and located radially outwardly of the first gas outlet, the second gas outlet configured to inject a second gas in a swirling motion, the swirling motion intersecting the first direction to induce a mixing of the first gas and of the second gas for combustion of a mixture by the flame; an air circuit in fluid communication with one of the first gas outlet and the second gas outlet; and a synthesis gas circuit with the other of the first gas outlet and the second gas outlet; wherein the first gas is one of the air and the synthesis gas, and the second gas is the other of the air and the synthesis gas. A method for burning a synthesis gas obtained from biomass thermal treatment is also provided.

Description

BURNER SYSTEM FOR BIOMASS SYNTHESIS GASESCROSS-REFERENCE TO RELATED APPLICATION

[0001] The present application claims the priority of United States Patent Application No. 63 / 662,842, filed on June 21 , 2024, the content of which is incorporated hereby reference.TECHNICAL FIELD

[0002] The present disclosure relates to a system for combustion of a mixture of air and synthesis gases, also known as syngas, which synthesis gas are generated by the thermal treatment of biomass.BACKGROUND

[0003] Synthesis gases, also known as syngas or syngases, are used for numerous applications, such as chemical production, industrial processes and in some cases as fuel. Being a mixture that may include hydrogen, carbon monoxide, carbon dioxide and / or methane, synthesis gases usually have a high chemical energy potential and are generally unexpensive to produce. Synthesis gases may be a by-product of the thermal treatment of biomass, whether it be as a result of pre-drying, drying, torrefaction, charring, pyrolysis, to name a few non-exclusive possibilities. Existing system for generating and burning synthesis gases are satisfactory, but improvements are always sought.SUMMARY

[0004] In accordance with a first aspect, there is provided a system for burning a synthesis gas obtained from biomass thermal treatment, comprising: a combustor having a central axis and including a combustion head, the combustion head having: a central flame outlet configured to emit a flame, a first gas outlet extending around the central axis and located radially outwardly of the central flame outlet relative to the central axis and configured to inject a first gas into the combustor along a first direction having an axial component relative to the central axis, and a second gas outlet extending around the central axis and located radially outwardly of the first gas outlet, the second gas outlet configured to inject a second gas in a swirling motion, the swirling motion intersecting the first direction to induce a mixing of the first gas and of the second gas for combustion of a mixture by the flame; an air circuit in fluid communication with one of the first gas outlet and the second gas outlet; and a synthesis gas circuit with the other of the first gas outlet and the second gas outlet; wherein the first gas is one of the air and the synthesis gas, and the second gas is the other of the air and the synthesis gas.

[0005] Further in accordance with the first aspect, for instance, the combustor includes: an end wall defining an aperture; a flame outlet wall defining the central flame outlet and extending transversally to the end wall and communicating with the aperture; and an inner wall extending away from the end wall, the first gas outlet defined radially between the flame outlet wall and the inner wall.

[0006] Still further in accordance with the first aspect, for instance, the inner wall has a frustoconical shape and extends towards the central axis away from the end wall.

[0007] Still further in accordance with the first aspect, for instance, an outer wall protruding away from the end wall, the outer wall may be located radially outwardly of the inner wall relative to the central axis, the second gas outlet defined between the outer wall and the inner wall, the outer wall having a frustoconical shape.

[0008] Still further in accordance with the first aspect, for instance, fins may be disposed between the outer wall and the inner wall, the fins circumferentially distributed around the central axis and being angled to induce the swirling motion.

[0009] Still further in accordance with the first aspect, for instance, one of the air circuit and the synthesis gas circuit includes: an annular channel extending around the central axis and communicating with the first gas outlet via conduits circumferentially distributed around the central axis and extending radially inwardly from the annular channel.

[0010] Still further in accordance with the first aspect, for instance, the other of the air circuit and the synthesis gas circuit includes: an annular cavity extending around the central axis and communicating with the second gas outlet via passages defined between the conduits.

[0011] Still further in accordance with the first aspect, for instance, a cooling gas circuit may be fluidly connectable to a source of a cooling gas, the cooling gas circuit having a cooling gas outlet fluidly connected to a cavity of the combustion head.

[0012] Still further in accordance with the first aspect, for instance, the cooling gas circuit includes: conduits circumferentially distributed around the central axis leading to the cavity, the conduits located radially outwardly of the first gas outlet and the second gas outlet.

[0013] Still further in accordance with the first aspect, for instance, the cooling gas circuit further includes: an annular plenum extending around the central axis, each of the conduits having an inlet fluidly connected to the annular plenum.

[0014] Still further in accordance with the first aspect, for instance, a shield may have a conical shape and positioned onto the central flame outlet.

[0015] Still further in accordance with the first aspect, for instance, a combustion chamber may be in fluid communication with the combustion head, the combustion chamber extending along a chamber axis being parallel to the central axis.

[0016] Still further in accordance with the first aspect, for instance, the combustion chamber extends parallel to a ground.

[0017] Still further in accordance with the first aspect, for instance, the combustion chamber has a peripheral wall enclosing a combustion cavity, the peripheral wall including an outer casing enclosing a layered structure, the layered structure including: a first layer of refracting bricks; and a second layer of refracting bricks located outwardly of the first layer relative of the central axis.

[0018] Still further in accordance with the first aspect, for instance, the layered structure further includes: a third layer of wool disposed around the second layer of refracting bricks.

[0019] Still further in accordance with the first aspect, for instance, the combustion chamber has at least two sections, a first section of the two sections being an upstream-most section of the combustion chamber, the layered structure located solely in the first section.

[0020] Still further in accordance with the first aspect, for instance, in a second section of the at least two sections, the peripheral wall includes the outer casing and a layer of wool disposed inwardly of the outer casing.

[0021] In accordance with a second aspect of the present disclosure, there is provided a method for burning a synthesis gas obtained from biomass thermal treatment, comprising: receiving a first gas and a second gas, wherein the first gas is one of air and the synthesis gas, the second gas is the other of air and the synthesis gas; injecting the first gas annularly around a flame and along a first direction intersecting the flame; and injecting the second gas annularly around the first gas and along a second direction intersecting the first gas and having a component in a circumferential direction relative to an axis parallel to a direction of the flame.

[0022] Still further in accordance with the second aspect, for instance, a cooling gas may be injected radially outwardly of the first gas and the second gas relative to the axis.

[0023] Still further in accordance with the second aspect, for instance, the injecting of the second gas along the second direction having the component in the circumferential direction includes: imparting the component in the circumferential direction using fins circumferentially distributed around the axis.DESCRIPTION OF THE DRAWINGS

[0024] Reference is now made to the accompanying figures in which:

[0025] Fig. 1 is a perspective view of a burner system for burning a synthesis gas;

[0026] Fig 2 is a perspective view of a combustor of the burner system of Fig. 1 ;

[0027] Fig. 3 is a three dimensional cutaway view of the combustor of Fig. 2;

[0028] Fig 4 is a cross-sectional view of the combustor Fig. 2;

[0029] Fig 5 is a perspective view of another embodiment of a combustor for the burner system of Fig. 1;

[0030] Fig. 6 is a three dimensional cutaway view of the combustor of Fig. 5;

[0031] Fig. 7 is a three dimensional cutaway view of the combustor of Fig. 5;

[0032] Fig. 8 is a three dimensional view of the combustion chamber of Fig. 1 ;

[0033] Fig. 9 is a cross-sectional view of the combustion chamber of Fig. 8 taken across either a proximal or medial section thereof;

[0034] Fig. 10 is a cross-sectional view of the combustion chamber of Fig. 8 taken across a distal section thereof; and

[0035] Fig. 11 is a flowchart illustrating steps of a method of burning a synthesis gas in accordance with another aspect of the present disclosure.

[0036] Many further features and combinations thereof concerning the present improvements to those skilled in the art following a reading of the instant disclosure.DETAILED DESCRIPTION

[0037] In the context of torrefaction of biomass, products of increased calorific value are produced by thermal treatment of the biomass. In this treatment, the biomass is heated, which leads to the reduction of mass and of the water content therein. As such, drying gases with high temperature may be used to dehumidify and dry the biomass. One method for producing the drying gases is to burn a mixture of air and synthesis gases, which yields a gas having a high temperature. In order to efficiently torrefy biomass, various mechanisms in the systems for thermally treating biomass may be optimized to minimize energy losses, and to ensure uniform burning of the synthesis gases, considering that the synthesis gases are a blend of different gases that may have different combustion characteristics. The burner system that produces the drying gases generally needs to be cooled to prevent the burner from overheating. Furthermore, the production rate of drying gases, which is usually limited by the configuration of the burner, may affect the overall temperature inside the combustion chamber. The present disclosure pertains to burner systems that may at least partially alleviate these drawbacks.

[0038] Referring to the drawings and more particularly to Fig. 1 , there is shown an exemplary system 1 for burning a synthesis gas. The system 1 includes a combustor 2 including a combustion chamber 3. The system 1 receives synthesis gas from a synthesis gas source 5 and air from an air source 6. In some embodiments, the system 1 receives reused combusted gas from a cooling gas source 7, and a fuel from a fuel source 8. As depicted in Fig. 1 , the combustor 2 includes a combustion head 10 that is configured for mixing air with synthesis gas next to a flame, thereby producing drying gas burning within the combustor 2, such as in the combustion chamber 3. The system 1 may be in fluid communication with a system for thermal treatment of biomass, which uses the drying gas produced by the combustor 2 to dry, dehumidify the biomass, stated differently to reduce a moisture content in the biomass. In some cases, the combustion chamber 3 is in fluid communication with an input of the system for torrefaction of biomass. The synthesis gas may be defined as being a mixture of hydrogen and carbon monoxide, among other possible gases, and may be output from a cellulose drying or process, or like process in which humidity is removed from biomass.

[0039] The synthesis gas source 5 may be a pipe network feeding the system 1 with synthesis gas from an external source. The air source 6 may include one or more pipe network providing a particular air mixture from one or more segments of a process, or an air intake that draws air surrounding the system 1 , such as outdoor air, pre-heated air, etc. In some embodiments, the airfrom the source 6 may include a non-volatile gas, or a mixture of the latter and air, in order to reduce the heat created by the ignition of the mixture of air and synthesis gas in the combustor 2 by reducing the combustion rate. It may also include a gas that is generally inert, in that it has a low oxygen content. The cooling gas source 7 may also be embodied by a pipe network that recuperates heat from a process, such as used drying gas. Thus, the cooling gas source 7 may be the output of another system 1 for burning a synthesis gas, which may be connected by a pipe network. In this case, the pipe network may be cooled so that the gas produced by the other system 1 has a reduced temperature compared to the desired temperature for an output gas. Stated differently, the cooling gas source 7 may come directly from the process, or may be cooled by any appropriate heat exchanger. The fuel source 8 may be embodied as a pipe feeding a flammable gas into the system. As will be further described below, the fuel source 8 may have various shape and may be optional, in accordance with the implementation.

[0040] The combustion head 10 may be releasably attached to the combustion chamber 3, or welded or bolted to the combustion chamber 3. In some embodiments, the combustion head 10 is integral with the combustion chamber 3. While the combustion chamber 3 has a cylindrical shape as shown in Fig. 1 , it will be appreciated that the size and shape of the combustion chamber 3 may vary according to the implementation.

[0041] Fig. 1 is an exemplary representation of the system 1 , but is only given as an example. The system 1 is configured to receive a synthesis gas feed from a process, and may also draw in air, whether it be ambient air or air from a process, to mix the air with the synthesis gas. When using the expression “air” herein, the present disclosure refers to a mixture of gases that includes oxygen, in a suitable proportion to allow combustion of the mixture of gases when mixed with fuel, i.e., the synthesis gas. In a variant, the synthesis is depleted from oxygen, or has a low oxygen content, such that the oxygen in the air compensates for the oxygen deficiency in the synthesis gas when mixed thereto, to induce combustion of the synthesis gas.

[0042] Now referring to Fig. 2, there is shown a perspective view of a combustion head 10 of the system 1 for burning a synthesis gas, in accordance with one or more embodiments. The combustion head 10 may have a head cavity 11 defined conjointly by an end wall 12 and a lateral wall 13. The end wall 12 is shown having a circular flat surface, as an example among other shapes. Other shapes are contemplated, such as square, triangular, elliptical, and the like, and the end wall 12 need not be flat (e.g., co-planar). The lateral wall 13 projects transversally to the end wall 12. The lateral wall 13 may project orthogonally or with an angle, from an outer perimeterof the end wall 12, though this is just an example. While an edge is shown demarcating the end wall 12 from the lateral wall 13, there may be no edge. It is thus understood that the lateral wall13 generally has a cylindrical shape but this is merely exemplary for the sake of illustration. An annular flange, or simply a flange 14 extends transversally to a distal end of the lateral wall 13. Put differently, the lateral wall 13 is located between the end wall 12 and the flange 14. The flange14 may extend radially outwardly relative to a central axis A1 of the combustion head 10. The flange 14 may have coupling means 15 configured to match with a corresponding coupling section on the combustion chamber 3. The coupling means 15 may be a circumferential distribution of holes, such as for receiving bolts, an interlocking mechanism, a weld, and other coupling of the like. Therefore, when attached to the combustion chamber 3 - that may have a matching flange -, the flange 14 of the combustion head 10 abuts the combustion chamber 3 around an inner cavity of the combustion chamber 3, such that the head cavity 11 is in fluid communication with the inner cavity of the combustion chamber 3. In other words, the end wall 12 and the cavity 11 face the combustion chamber 3 once the combustion head 10 is mounted thereto. The flange 14 is optional, or may be located much farther away from the end wall 12.

[0043] The combustion head 10 may further include a combustion unit 20 integrated in the end wall 12, as depicted in Figs. 2 and 3, the latter showing a cross-section of a perspective view of the combustion head 10. The combustion unit 20 has a central flame outlet 21 for emitting a flame in a direction of propagation A that is substantially parallel to the central axis A1 and transversal to the end wall 12, toward the combustion chamber 3. In the context of the present disclosure, the expression “substantially” as in “substantially parallel” implies slight deviations from perfectly parallel caused by manufacturing tolerances for instance. In operation, the flame emitted by the central flame outlet 21 is positioned to ignite the mixture of synthesis gas and air that is directed toward the direction of propagation A, to burn the mixture. The central flame outlet 21 has a flame outlet wall 22, which may be tubular and optionally concentric with the lateral wall 13 of the combustion head 10. The source of the flame emitted by the central flame outlet 21 may be of various kind, for instance a source of ignition gas, a source of plasma, a heat lamp, a laser, and other kind of combustion trigger, or any appropriate means to cause the combustion of the mixture of synthesis gas and air. It will be appreciated that the combustion trigger is selected so that it provokes the ignition of the air and syngas mixture.

[0044] The central flame outlet 21 may further include all necessary components to produce a flame. Figs. 6 and 7 show exemplary components, that may include a pipe(s) for provide amixture of air and fuel, and a pilot flame. Other components may be present, so long as a flame is produced at or near the exit of the central flame outlet 21 , in the direction of propagation.

[0045] The combustion unit 20 may also include an inner gas outlet 23 and an outer gas outlet 24, each optionally being concentric with the central flame outlet 21 and having at least an axial component relative to the central axis A1 , so that the gases outputted by the inner gas outlet 23 and the outer gas outlet 24 are directed at least partially along the direction A. As best seen in Fig. 3, the inner gas outlet 23 forms an annular passage around the flame outlet wall 22, and the outer gas outlet 24 forms an annular passage around the first gas outlet 23.

[0046] The annular passage of the inner gas outlet 23 may correspond to a gap between edges of the flame outlet wall 22 and of an inner frustoconical wall 25a. While the inner frustoconical wall 25a is shown having a frustoconical geometry, other geometries are considered, including cylindrical. As explained below, the frustoconical shape of the inner frustoconical wall 25a may contribute to directing a flow of gas toward a center of the combustion head 10, for the gas exiting the first gas outlet 23, and possibly the gas exiting the second gas outlet 24. In other words, having the frustoconical shape allows to impart a direction to the gas having both of an axial and a radially-inward component relative to the central axis A1. Thus, the gas may be directed towards the flame, which may improve combustion efficiency.

[0047] In some embodiments, the outer gas outlet 24 is defined by the inner frustoconical wall 25a and an outer frustoconical wall 25b extending from the end wall 12 of the combustion head 10. In the depicted embodiment, the inner frustoconical wall 25a is located radially inwardly of the outer frustoconical wall 25b relative to the central axis A1. It may be said that the outer gas outlet 24 has a tapered member 25 defined conjointly by the walls 25a, 25b. The free edges of the inner frustoconical wall 25a and of the outer frustoconical wall 25b are radially spaced apart from one another to define therebetween the annular passage of the outer gas outlet 24. Other geometries are possible, but the tapered member 25 defines a fluid path that extends in the direction A and towards the center of the combustion unit 20, thereby directing the gas outputted by the second gas outlet 24 towards the center of the combustion unit 20. For example, in the cross-section of Fig. 3 taken on a plane containing the central axis A1 , it can be seen that the frustoconical walls 25a and 25b are at an angle T 1 ranging between 20 and 70 degrees toward the central axis A1 . While the embodiment depicted in Figs. 2 and 3 show the combustion unit 20 positioned at the center of the combustion head 10, it will be appreciated that the combustion unit 20 may be decentered in the combustion head 10, in accordance with the implementation. In someembodiments, as described further below, a plurality of fins 26 project from the inner conical wall 25a to induce a swirl motion in the gas outputted by the second gas outlet 24. Put differently, the fins 26 are circumferentially distributed around the central axis A1 and are located within the outer gas outlet 24. The fins 26 are angled to induce a swirling motion of the gas that flows between them. In other words, the fins 26 extend from upstream ends to downstream ends; the upstream ends being circumferentially offset from the downstream ends relative to the central axis A1 to induce the swirl motion in the gas flowing between them. Similar fins may be located, in addition or in substitution, into the inner gas outlet 23 to induce a similar swirling motion. The fins 26 are optional.

[0048] Still in reference with Figs. 2 and 3, there is shown a first gas inlet 30 and a second gas inlet 40 in fluid communication to the combustion head 10. The first gas inlet 30 optionally includes a first coupler 31 . The first coupler 31 may be a duct or conduit, that may optionally have a tapered shape, the larger end of the first coupler 31 configured to connect to a gas source, such as the gas source 5 or the air source(s) 6. The tapered shape, while optional, may be used to accelerate the flow of gas in the first gas inlet 30. A first conduit 32 extends from the other end of the first coupler 31 and connects with the combustion unit 20. The end of the first conduit 32 opposite the end coupled to the first coupler 31 is in fluid communication with a first or outer channel 33 positioned on the side of the end wall 12 of the combustion head 10 that is away from the combustion chamber 3. The first channel 33 may have an annular shape and may be concentric with the combustion unit 20. In a variant, the first conduit 32 merges with the first channel 33 in a tangential manner, for the gas flowing into the first channel 33 to have a swirling motion. The first channel 33 may be delimited by the end wall 12 of the combustion head 10, as seen in Fig. 3, but this is optional. The first channel 33 is in fluid communication with a second or inner channel 34 via a plurality of first tubular conduits 35, though a single one may also be present. The conduits 35 are shown as being substantially radial in orientation relative to the central axis A1 , but other orientations are possible. The second channel 34 may also have an annular shape and may also be concentrical with the combustion unit 20. A side wall of the second channel 34 may be formed by the flame outlet wall 22, and the top of the second channel may be formed by the inner frustoconical wall 25a of the tapered member 25, as seen in Fig. 3. Other configurations are possible. The configuration of the first gas inlet 30, with a pair of annular channels 33 and 34, with fluid communication between them via conduits 35, is optional, but may contribute to maintaining a compact shape for the combustion head 10. As an alternativeembodiment, the first conduit 32 may be connected directly to the channel 34, i.e., without the annular channel 33 or the tubular conduits 35.

[0049] It is understood that the radius of the first channel 33 corresponds to the radius of the second channel 34 plus the length of the first tubular conduits 35. The first channel 33 defines a plurality of apertures angularly aligned with respective apertures defined in the second channel34, thereby forming pairs of aligned apertures, and a respective first tubular connector 35 fluidly connects each pairs of aligned apertures. As such, spaces are defined between the first tubular conduits 35, which enable gas to propagate around the plurality of first tubular conduits 35, namely between a space below the first tubular conduits 35 and a space above the first tubular conduits35. In operation, when gas is injected in the first gas inlet 30, the gas propagates in the first coupler 31 if present and may be accelerated therein, then to the first channel 33 through the first conduit 32, then to the second channel 34 through the first tubular conduits 35, then out into the combustion chamber 3 via the first gas outlet 23.

[0050] In a similar fashion, the second gas inlet 40 optionally includes a second coupler 41 having a tapered shape, the larger end of the second coupler 41 configured to connect to a gas source, such as the synthesis gas source 5 or the gas source 6. Again this is optional. A second conduit 42 extends from the other end of the second coupler 41 and connects with the combustion unit 20. The end of the second conduit 42 opposite the end coupled to the second coupler 41 is in fluid communication with a gas cavity 43, which extends radially between the flame outlet wall 22 and a cavity wall 44. In a variant, the second conduit 42 merges with the cavity wall 44 in a tangential manner, for the gas flowing into the first channel 33 to have a swirling motion, but this is optional. The gas cavity 43 is delimited by the end wall 12 of the combustion head 10, and end wall 45. In operation, when gas is inserted in the second gas inlet 40, the gas propagates in the second coupler 41 if present, then to the gas cavity 43 through the second conduit 42, then to the outer gas outlet 24 by passing through the spaces formed between the first tubular conduits 35, if present.

[0051] In some embodiments, as shown in Fig. 4, which depicts a cross-sectional view of the combustion head 10 taken on a plane normal to the central axis A1 , the plurality of fins 26 project from the inner frustoconical wall 25a of the tapered member 25. When gas is outputted via the outer gas outlet 24, the plurality of fins 26 assist in deviating the flow of gas in a swirl motion. As the outer gas outlet 24 radially surrounds the inner gas outlet 23, the mixture of gas outputted by both outlets 23, 24 is entrained by the swirl created by the plurality of fins 26. It will be appreciatedthat the flow of swirled gas may have a generally conical direction, as the outer gas outlet 24 is circular and as the tapered member 25 causes the gas outputted by the outer gas outlet 24 to be directed towards the central axis and in the direction A, which is substantially parallel to the central axis A1.

[0052] The plurality of fins 26 may be protrusions extending outwardly from the inner frustoconical wall 25a of the tapered member 25 towards the outer frustoconical wall 25b thereof, as an option among others. The plurality of fins 26 may have various types of shape, according to the implementation. For instance, the shape of the surface of the plurality of fins 26 may be rectangular, triangular, semi-circular or irregular. The shape of the surface of the plurality of fins 26 may also be curved in a tridimensional manner to improve the swirl motion. Each fin 26 may be radially aligned with the center of the combustion unit 20, shifted by a predefined angle, or a combination thereof for the plurality of fins 26, but this is optional as numerous other arrangements are considered. It will be also appreciated that the number of fins 26 may vary, and is not limited to the depicted embodiment. For instance, the combustor 2 may include a single fin 26, five fins 26, ten fins 26, twenty-five fins 26, fifty fins 26 or a hundred of fins 26.

[0053] The gas outputted by one of the inner gas outlet 23 and the outer gas outlet 24 may be air while synthesis gas may be outputted by the other of the inner gas outlet 23 and the outer gas outlet 24. In some embodiments, the gas outputted by the inner gas outlet 23 is air, and the gas outputted by the outer gas outlet 24 is synthesis gas. In a variant, there is a greater volumetric flow of synthesis gas than of air. It may be preferred to inject the gas with the greater volumetric flow via the second gas outlet 24, to create a more efficient mixture of air and synthesis gas, which synthesis gas is the fuel. Also, in the embodiment shown, the air and the synthesis gas are injected in opposite rotational directions relative to the central axis A1 (e.g., clockwise and counter-clockwise).

[0054] In some embodiments, having the two outlets 23, 24 concentric may allow for an improved mixing of the synthesis gas and the air. This, in turn, may promote an efficient combustion. The swirl motion induced by the optional fins 26 may further enhance the mixing between the air and the synthesis gas, which may further promote the combustion efficiency. Having the air and the synthesis gas injected in intersecting directions or flows may favor heat transfer as one of the air and the synthesis gas flows around the first tubular conduits 35, in which flows the other of the air and the synthesis gas. This may also promote efficient combustion. The swirl or vortex created by the fins 26 or equivalent passageway (e.g., baffle plates, channels, etc)may increase residence time in the combustion chamber, which may improve a mixing of the air and the synthesis gas, which in turn may improve combustion of the synthesis gas.

[0055] Now referring to Figs. 5 and 6, there is shown a perspective view of another variant of the combustion head 10 of the system 1 for burning a synthesis gas, the combustor 2 including a cooling gas circuit 50 including a third gas inlet for receiving cooling gas. The cooling gas may be extracted or recuperated from a process. In an embodiment, it is called a cooling gas as it may be relatively colder than the other gases in the combustion chamber 3. The cooling gas may be said to be inert, in that it may have a low oxygen content (e.g., flux gas). In this configuration, the combustion head 10 is fed with cooling gas that is injected in periphery of the combustion unit 20, which helps reduce thermal stresses on the walls of the combustion chamber 3 by limiting the heat generated by the combustion to the center of the combustion head 10.

[0056] As shown in Fig. 6, the interior of the central flame outlet 21 has a liner of frustoconical shape expending in the direction A, which causes the flame to spread outwardly in the head cavity 11 , while shielding the flame outlet wall 22. As mentioned above, such liner may be present in the combustion head 10 of Figs. 2 and 3. Such configuration may improve the combustion efficiency of the mixture by increasing the volume of which the flame is in contact with the mixture. A refractory liner 11a may be present as well, as shown. As mentioned above, such refractory liner 11a may be present in the combustion head 10 of Figs. 2 and 3. Other burner components are illustrated as well, such as the fuel source 8 in which a flammable gas is fed in the combustion unit 20, and are used to create a flame at the central flame outlet 21.

[0057] The cooling gas circuit 50 optionally includes a third coupler 51 having a tapered shape, the larger end of the third coupler 51 configured to connect to the cooling gas source 7. A third conduit 52 extends from the other end of the third coupler 51 and connects with the combustion head 10. The end of the third conduit 52 opposite the end coupled to the third coupler 51 is in fluid communication with a third channel 53, which may be referred to as an annular plenum, positioned adjacent to end wall 45 of the gas cavity 43. The third channel 53 may have an annular shape and may be concentrical with the combustion unit 20. The third channel 53 is delimited by the end wall 45 of the gas cavity 43, as seen in Figs. 6 and 7, but this is optional. In the embodiment shown, the end wall 45 defines a series of apertures 45a circumferentially distributed around the central axis and each communicating with the third channel 53. A plurality of second tubular conduits 54 protrude from the end wall 45 and are each in register with a respective one of the apertures 45a. The second tubular conduits 54 may extend axially relativeto the central axis A1 towards the head cavity 11 . The plurality of second tubular conduits 54 are circumferentially distributed around the central axis A1 , and may be located radially inwardly of the cavity wall 44. The conduits 54 are leading to the cavity 11 and may be located radially outwardly of the inner and outer gas outlets 23, 24. The plurality of second tubular conduits 54 extend through the gas cavity 43, the first channel 33 and the end wall 12 of the combustion head 10, which creates a fluid communication between the head cavity 11 and the third channel 53.

[0058] In operation, when cooling gas in inserted in the combustor 2, the cooling gas propagates in the third coupler 51 , then to the third channel 53 through the third conduit 52, then to the head cavity 11 via the second tubular conduits 54, via nozzles 55 or like outlets for the tubular conduits 54. It will be appreciated that the number of second tubular conduits 54 may vary, and is not limited to the depicted embodiment. It can be observed that the second tubular conduits 54 and the nozzles 55 are oriented to be parallel with direction A and the central axis A1 . While other orientations are possible, this illustrated arrangement is suitable in that it reduces the interaction between the injected cooling gas and the vortex created by the combustion unit 20. Hence, the injected cooling gas may from a cooling gas curtain between the burning vortex and the wall of the combustor 2.

[0059] In some embodiments, as presented in Fig. 7, the combustion head 10 may be equipped with a shield 27, which covers the combustion unit 20. The shield 27 may be received between the combustion unit 20 and the end wall 12. The shield 27 defines apertures 28 therethrough for receiving the gas that flows within the first tubular conduits 35.

[0060] Referring now to Fig. 8, the combustion chamber 3 is described in greater detail with reference numerals in the 80’s. The chamber 3 includes three sections, namely, a proximal section 81 , a medial section 82, and a distal section 83 in relation to a distance from the combustion head 10, the combustion head 10 being fixed to the proximal section 81. As shown in Fig. 9, the proximal and medial sections 81 , 82 may be part of an upstream-most section of the chamber 3 and have a layered structure 84 including a first layer 85, which may be made of refractive bricks, such as GREENTHERM 26AM™, having a thickness of about 4.5 inches, a second layer 86, which may be made of refractive bricks, such as GREENTHERM 23AM™, having a thickness of about 4.5 inches, a third layer 87, which may be made of wool, such as INSWOOL 2300 PAPER™, having a thickness of about 0.25 inch, and a fourth layer 88, which may be made of ceramic fibers, such as INSBOARD 2300 HD™, having a thickness of about 3 inches. These types of refractory bricks are merely an option among others. The layered structure84 may be located solely in proximal and medial sections 81 , 82. It will be appreciated that the thickness of the different layer may be adjusted. The combustion chamber 3 further includes an outer casing 89 that surrounds the layered structure 84. The outer casing 89 may be made of a metallic material. The first layer 85 is surrounded by the second layer 86, which is surrounded by the third layer 87, which is itself surrounded by the fourth layer 88. An inner diameter of the combustion chamber 3 may be about 7 feet. In the context of the present disclosure, the expression “about” implies variations of plus or minus 10%. Having two layers of refracting bricks may increase a thermal inertia of the combustion chamber 3, which may reduce a temperature of the outer casing 89 to about at most 60 degrees Celsius in some embodiments. It will be appreciated that the proximal and distal sections 81 , 82 may be combined in a single section of a greater length. Having three sections may facilitate shipping and installation of the combustion chamber 3. Referring now to Fig. 10, the distal section 83 may include a single layer of wool. In the embodiment shown, a length of the distal section 83 is greater than that of each of the proximal and medial sections 81 , 82. Other configurations are contemplated.

[0061] Referring to Fig. 11 , a method for burning a synthesis gas is shown at 1100. The method 1100 includes: receiving a first gas and a second gas, wherein the first gas is one of air and the synthesis gas, the second gas is the other of air and the synthesis gas at 1102; injecting the first gas annularly around the flame and along a first direction intersecting the flame at 1104; and injecting the second gas annularly around the first gas and along a second direction intersecting the first gas and having a component in a circumferential direction relative to the central axis A1 , which is parallel to a direction of the flame at 1106.

[0062] In some embodiments, the method further comprises: injecting a cooling gas radially outwardly of the first gas and the second gas relative to the axis. The injecting of the second gas along the second direction having the component in the circumferential direction may include: imparting the component in the circumferential direction using the fins 26 circumferentially distributed around the axis.

[0063] It is noted that various connections are set forth between elements in the preceding description and in the drawings. It is noted that these connections are general and, unless specified otherwise, may be direct or indirect and that this specification is not intended to be limiting in this respect. A coupling between two or more entities may refer to a direct connection or an indirect connection. An indirect connection may incorporate one or more intervening entities. The term “connected” or "coupled to" may therefore include both direct coupling (in whichtwo elements that are coupled to each other contact each other) and indirect coupling (in which at least one additional element is located between the two elements).

[0064] It is further noted that various method or process steps for embodiments of the present disclosure are described in the preceding description and drawings. The description may present the method and / or process steps as a particular sequence. However, to the extent that the method or process does not rely on the particular order of steps set forth herein, the method or process should not be limited to the particular sequence of steps described. As one of ordinary skill in the art would appreciate, other sequences of steps may be possible. Therefore, the particular order of the steps set forth in the description should not be construed as a limitation.

[0065] Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. As used herein, the terms “comprises”, “comprising”, or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0066] While various aspects of the present disclosure have been disclosed, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible within the scope of the present disclosure. For example, the present disclosure as described herein includes several aspects and embodiments that include particular features. Although these particular features may be described individually, it is within the scope of the present disclosure that some or all of these features may be combined with any one of the aspects and remain within the scope of the present disclosure. References to “various embodiments,” “one embodiment,” “an embodiment,” “an example embodiment,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. The use of the indefinite article “a” as used herein with reference to a particular element is intended to encompass “one or more” such elements, and similarly the use of the definite article “the” in reference to a particular element is not intended to exclude the possibility that multiple of such elements may be present.

[0067] The embodiments described in this document provide non-limiting examples of possible implementations of the present technology. Upon review of the present disclosure, a person of ordinary skill in the art will recognize that changes may be made to the embodiments described herein without departing from the scope of the present technology. Yet further modifications could be implemented by a person of ordinary skill in the art in view of the present disclosure, which modifications would be within the scope of the present technology.

Claims

CLAIMS1. A system for burning a synthesis gas obtained from biomass thermal treatment, comprising: a combustor having a central axis and including a combustion head, the combustion head having: a central flame outlet configured to emit a flame, a first gas outlet extending around the central axis and located radially outwardly of the central flame outlet relative to the central axis and configured to inject a first gas into the combustor along a first direction having an axial component relative to the central axis, and a second gas outlet extending around the central axis and located radially outwardly of the first gas outlet, the second gas outlet configured to inject a second gas in a swirling motion, the swirling motion intersecting the first direction to induce a mixing of the first gas and of the second gas for combustion of a mixture by the flame; an air circuit in fluid communication with one of the first gas outlet and the second gas outlet; and a synthesis gas circuit with the other of the first gas outlet and the second gas outlet; wherein the first gas is one of the air and the synthesis gas, and the second gas is the other of the air and the synthesis gas.

2. The system of claim 1 , wherein the combustor includes: an end wall defining an aperture; a flame outlet wall defining the central flame outlet and extending transversally to the end wall and communicating with the aperture; and an inner wall extending away from the end wall, the first gas outlet defined radially between the flame outlet wall and the inner wall.

3. The system of claim 2, wherein the inner wall has a frustoconical shape and extends towards the central axis away from the end wall.

4. The system of claim 2 or 3, comprising an outer wall protruding away from the end wall, the outer wall located radially outwardly of the inner wall relative to the central axis, the second gas outlet defined between the outer wall and the inner wall, the outer wall having a frustoconical shape.

5. The system of claim 4, comprising fins disposed between the outer wall and the inner wall, the fins circumferentially distributed around the central axis and being angled to induce the swirling motion.

6. The system of any one of claims 1 to 5, wherein one of the air circuit and the synthesis gas circuit includes: an annular channel extending around the central axis and communicating with the first gas outlet via conduits circumferentially distributed around the central axis and extending radially inwardly from the annular channel.

7. The system of claim 6, wherein the other of the air circuit and the synthesis gas circuit includes: an annular cavity extending around the central axis and communicating with the second gas outlet via passages defined between the conduits.

8. The system of any one of claims 1 to 7, further comprising: a cooling gas circuit fluidly connectable to a source of a cooling gas, the cooling gas circuit having a cooling gas outlet fluidly connected to a cavity of the combustion head.

9. The system of claim 8, wherein the cooling gas circuit includes: conduits circumferentially distributed around the central axis leading to the cavity, the conduits located radially outwardly of the first gas outlet and the second gas outlet.

10. The system of claim 9, wherein the cooling gas circuit further includes: an annular plenum extending around the central axis, each of the conduits having an inlet fluidly connected to the annular plenum.11 . The system of any one of claims 1 to 10, further comprising: a shield having a conical shape and positioned onto the central flame outlet.

12. The system of any one of claims 1 to 11 , comprising a combustion chamber in fluid communication with the combustion head, the combustion chamber extending along a chamber axis being parallel to the central axis.

13. The system of claim 12, wherein the combustion chamber extends parallel to a ground.

14. The system of claim 12 or 13, wherein the combustion chamber has a peripheral wall enclosing a combustion cavity, the peripheral wall including an outer casing enclosing a layered structure, the layered structure including: a first layer of refracting bricks; and a second layer of refracting bricks located outwardly of the first layer relative of the central axis.

15. The system of claim 14, wherein the layered structure further includes: a third layer of wool disposed around the second layer of refracting bricks.

16. The system of claim 14 or 15, wherein the combustion chamber has at least two sections, a first section of the two sections being an upstream-most section of the combustion chamber, the layered structure located solely in the first section.

17. The system of claim 16, wherein, in a second section of the at least two sections, the peripheral wall includes the outer casing and a layer of wool disposed inwardly of the outer casing.

18. A method for burning a synthesis gas obtained from biomass thermal treatment, comprising: receiving a first gas and a second gas, wherein the first gas is one of air and the synthesis gas, the second gas is the other of air and the synthesis gas; injecting the first gas annularly around a flame and along a first direction intersecting the flame; and injecting the second gas annularly around the first gas and along a second direction intersecting the first gas and having a component in a circumferential direction relative to an axis parallel to a direction of the flame.

19. The method of claim 18, further comprising:injecting a cooling gas radially outwardly of the first gas and the second gas relative to the axis.

20. The method of claim 18 or 19, wherein the injecting of the second gas along the second direction having the component in the circumferential direction includes: imparting the component in the circumferential direction using fins circumferentially distributed around the axis.

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