Process for producing a synthesis gas product containing hydrogen - Patent Application 20070122997

Abstract

1. A method for producing a synthesis gas product comprising hydrogen by an endothermic reaction of a feedstock, the method comprising the steps of: supplying a first fuel gas comprising at least 20% ammonia to a combustion chamber at a first flow rate; supplying a second fuel gas comprising at least 10% hydrogen to the combustion chamber at a second flow rate, wherein at least a first portion of one of the fuel gases is delivered to the combustion chamber separately from the other fuel gas; supplying an oxidizing gas stream; and performing combustion of the supplied first fuel gas and the supplied second fuel gas together with the supplied oxidizing gas stream in the combustion chamber to provide heat to the endothermic reaction.

Description

[Technical Field]

[0001] The field of the invention is that of processes for producing a synthesis gas product comprising hydrogen by endothermic reaction of a feedstock. The invention also relates to a burner assembly for inputting heat into an endothermic reactor. The invention is also directed to a furnace including one or more burner assemblies. The invention also relates to the use of such a burner assembly. [Background technology]

[0002] The production of synthesis gas containing hydrogen by endothermic reactions of the feed stream requires heat, which is typically provided by the combustion reaction of fuel gas in a furnace to heat the ammonia feedstock.

[0003] The drawbacks of ammonia as a fuel are its poor combustion characteristics, i.e. low flame speed, small ignition and explosion windows, and high ignition temperature, which lead to flame instability and the generation of unconverted ammonia and NO. X This results in undesirable emissions such as:

[0004] More stable flame, flame speed and NO X There are several ways to improve the combustion behavior, such as mixing other fuels, e.g., hydrogen, to improve the effect of the formation. However, to ensure flame stability, it is necessary to maintain the fuel tip gas exit velocity over the full operating window of the appliance in a certain range close to the flame speed of the gas mixture. Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention proposes a method for producing synthesis gas products containing hydrogen by endothermic reaction of a feedstock that ensures a stable hydrogen fuel / ammonia fuel ratio to avoid flame instability, flame lift-off, and possible eventual flame extinguishing, thereby improving the combustion of ammonia fuel and subsequently converting the feedstock into better synthesis products containing hydrogen. [Means for solving the problem]

[0006] To this end, the present invention proposes a method for producing a synthesis gas product, in particular a synthesis gas product comprising hydrogen, by endothermic reaction of a feedstock, said method comprising the following steps: - supplying a first fuel gas containing at least 20% ammonia to a combustion chamber at a first flow rate; - supplying a second fuel gas comprising at least 10% hydrogen to the combustion chamber at a second flow rate, wherein at least a first portion of one of the fuel gases is delivered to the combustion chamber separately from the other fuel gas; - providing an oxidizing gas flow; - performing combustion in a combustion chamber of the supplied first fuel gas and the supplied second fuel gas together with the supplied oxidizing gas stream to provide heat to the endothermic reaction; Includes:

[0007] In this disclosure, the ammonia fuel stream is also referred to as ammonia fuel.

[0008] In one embodiment of the present invention, the feedstock is an ammonia feedstock, and the endothermic reaction is an endothermic decomposition reaction of the ammonia feedstock.

[0009] In one aspect of the invention, the oxidizing gas comprises combustion air.

[0010] In one aspect of the invention, the step of supplying the second fuel gas includes separately delivering at least a first portion of the second fuel gas from the first fuel gas to the combustion chamber.

[0011] In one aspect of the invention, the step of supplying the second fuel gas includes separately delivering at least a first portion of the first fuel gas from the second fuel gas to the combustion chamber.

[0012] In one aspect of the invention, the combustion is carried out non-catalytically, in other words, without any catalyst to promote oxidation.

[0013] In one aspect of the invention, the combustion takes place in at least one baking appliance, the term baking appliance indicating that the second fuel takes place in the form of a flame.

[0014] In one aspect of the invention, the first fuel gas and the second fuel gas have different compositions.

[0015] In one aspect of the invention, the second fuel gas comprises at least 15% hydrogen, preferably at least 20%, preferably at least 30%, preferably at least 40%, preferably at least 50%, preferably at least 60%, preferably at least 70%, preferably at least 80%, preferably at least 90%, preferably up to 100% hydrogen.

[0016] In one aspect of the invention, the first fuel gas comprises at least 30% ammonia, preferably at least 40%, preferably at least 50%, preferably at least 60%, preferably at least 70%, preferably at least 80%, preferably at least 90%, preferably up to 100% ammonia.

[0017] In one aspect of the invention, first and second fuel gases and an oxidizing gas are mixed in a combustion chamber to obtain a combustion mixture.

[0018] In one aspect of the invention, combustion is achieved by igniting the combustion mixture.

[0019] In one aspect of the invention, three or more fuel gases are supplied to the combustion chamber, with at least one portion of one of each gas being delivered separately to said combustion chamber.

[0020] In one aspect of the invention, three or more fuel gases are supplied to the combustion chamber, each gas being delivered separately to said combustion chamber.

[0021] In one aspect of the invention, the method includes controlling a first flow rate of a first fuel gas and a second flow rate of a second fuel gas, whereby the velocity of each fuel gas supplied to the combustion chamber can be optimized to maintain a range close to the flame speed during the combustion step, thereby optimizing combustion.

[0022] Alternatively or in addition to controlling the first and second flow rates, the method may include supplying a second portion of one of the fuel gases, e.g., the second fuel gas, along with the other fuel gas, e.g., the first fuel gas, so that the second portion of the fuel gas, e.g., the second gas, is mixed with the other fuel gas, e.g., the first fuel gas. In one embodiment of the present invention, the second portion of one of the fuel gases supplied along with the other fuel gas is mixed with the other fuel gas, and then the first and second fuel gases and the oxidizing gas are mixed in the combustion chamber to obtain a combustion mixture. Specifically, supplying the second portion of one of the fuels, e.g., the second fuel gas, along with the other fuel gas, e.g., the first fuel gas, is controlled so that the mixed portion is comprised between 5% and 35%, preferably between 10% and 20%.

[0023] In one aspect of the present invention, the method includes supplying a second portion of a second fuel gas along with a first fuel gas, wherein the first fuel gas is mixed with the second portion of the second fuel gas. Specifically, supplying the second portion of the second fuel gas along with the first fuel gas is controlled so that the mixed portion of the second fuel gas in the first fuel gas is comprised between 5% and 35%, preferably between 10% and 20%.

[0024] Mixing one of the fuel gases, e.g., the first fuel gas, with a second portion of the other fuel gas, e.g., the second fuel gas, makes the flame more stable and thus allows for further optimization of the combustion behavior.

[0025] In one aspect of the invention, the second fuel gas delivers a hydrogen-rich fuel gas to the combustion chamber. In a preferred embodiment, the second fuel gas is injected into the first fuel gas to deliver the hydrogen-rich fuel gas to the first fuel gas.

[0026] This method ensures better flame stability during combustion, and the second fuel gas contains hydrogen, which stabilizes the flame.

[0027] In one aspect of the invention, an oxidizing gas is injected into the first and second fuel gases for combustion in the combustion chamber.

[0028] According to one aspect of the invention, the method includes the step of conditioning the feedstock, for example by evaporation, said conditioning step following the step of providing the feedstock.

[0029] According to one aspect of the present invention, an endothermic reaction converts the feedstock prepared in the preparing step into a synthesis gas product, particularly a synthesis gas product comprising hydrogen.

[0030] According to one aspect of the present invention, the synthesis gas product comprises hydrogen, nitrogen, and an unconverted portion of the ammonia feedstock that has not been converted after catalytic conversion of the ammonia feedstock.

[0031] According to one aspect of the invention, a method includes discharging a synthesis gas product from a reactor in which an endothermic reaction takes place.

[0032] According to one aspect of the invention, the method includes, following the releasing step, a step of treating the synthesis gas product. The treating step can be, for example, a purification step.

[0033] According to one aspect of the invention, the treating step is a purification step following the releasing step, said purification step using methods such as pressure swing adsorption (acronym PSA), cryogenic separation, membranes, temperature swing adsorption (acronym TSA).

[0034] According to one aspect of the invention, the step of preparing the feedstock comprises vaporizing, preheating or superheating the feedstock.

[0035] According to one aspect of the invention, heat for vaporizing, preheating or superheating the feedstock during the conditioning step is provided by an external heat source, such as an external calcination resulting from a combustion reaction near the conditioning step.

[0036] According to one aspect of the invention, the endothermic reaction is carried out in the presence of a catalyst that promotes catalytic conversion.

[0037] According to one aspect of the invention, the endothermic reaction is heated at least in part by combustion of a first fuel gas, a second fuel gas, and an oxidizing gas, as disclosed above.

[0038] The present invention also relates to a burner assembly for injecting heat into an endothermic reactor, the burner assembly comprising: - at least one oxidizing gas supply line configured to deliver an oxidizing gas stream to the combustion chamber of the furnace; a fuel gas supply line configured to deliver fuel gas to be combusted with an oxidizing gas in a combustion chamber, wherein: the first fuel gas supply line is configured to deliver a first fuel gas flow to the combustion chamber; the second fuel gas supply line is configured to deliver a second fuel gas stream to the combustion chamber, the second fuel gas supply line being configured to deliver the second fuel gas stream to the combustion chamber separately from the first fuel gas stream; The fuel gas mixing control device includes a fuel gas line arranged to mix a portion of one of the fuel gas streams with the other fuel gas stream in one of the first or second fuel gas supply lines.

[0039] In one aspect of the invention, the oxidizing gas is combustion air.

[0040] In one aspect of the invention, the second supply line is configured to deliver a first portion of the second fuel gas stream separately from the first fuel gas stream to the combustion chamber, and the fuel gas mixing control device is configured to mix the second portion of the second fuel gas stream with the first fuel gas stream in the first supply line.

[0041] In one aspect of the invention, the second supply line is configured to separately deliver a first portion of the first fuel gas stream from the second fuel gas stream to the combustion chamber.

[0042] In one aspect of the present invention, the fuel gas mixing control device includes a mixing valve disposed on one of the first or second supply lines, specifically a set of mixing valves disposed on at least one of the first or second supply lines.

[0043] In one aspect of the invention, the burner assembly is configured to supply a first fuel gas at a first flow rate and a second fuel gas at a second flow rate.

[0044] In one aspect of the invention, the burner is configured for non-catalytic combustion.

[0045] In one aspect of the invention, the burner is configured to produce combustion in the form of a flame, in other words, the burner is a firing appliance.

[0046] In one aspect of the invention, the first and second fuel gas flow supply lines are adjacent.

[0047] In one aspect of the invention, the first fuel gas supply line has a first flow cross section and the second fuel gas supply line has a second flow cross section.

[0048] In one aspect of the invention, the first and second fuel gas supply lines are separated by a liquid-tight layer.

[0049] In one aspect of the invention, the first and second fuel gas supply lines are arranged co-annulically.

[0050] In one aspect of the present invention, the first fuel gas supply line and the second fuel gas supply line are defined by cylindrical pipes, and the cylindrical pipe defining the second fuel gas supply line is combined within the cylindrical pipe defining the first fuel gas supply line.

[0051] In one aspect of the invention, the first and second fuel gas supply lines form an inner pipe.

[0052] In one aspect of the invention, the first flow cross section surrounds the second flow cross section.

[0053] In one aspect of the invention, the first flow cross section is ring-shaped.

[0054] In one aspect of the invention, the second flow cross section is ring-shaped.

[0055] This co-annular arrangement ensures better stabilization of the flame during combustion, and the second fuel gas contains hydrogen, which stabilises the flame.

[0056] In another aspect of the invention, the second flow cross section surrounds the first flow cross section.

[0057] According to one aspect of the invention, the oxidizing gas supply line is arranged co-annularly with the first and second fuel gas flow supply lines, specifically, the third flow cross section surrounds the first and second flow cross sections.

[0058] In one aspect of the invention, the first fuel gas supply line is configured to deliver an ammonia-rich fuel gas to the combustion chamber. In a preferred embodiment, the first fuel gas supply line is configured to deliver an ammonia-rich fuel gas stream, with the first flow cross-section surrounding the second flow cross-section.

[0059] In one aspect of the invention, the second fuel gas supply line is configured to deliver a hydrogen-rich fuel gas to the combustion chamber. In a preferred embodiment, the second fuel gas supply line, having a second flow cross-section surrounded by the first flow cross-section, is configured to deliver a hydrogen-rich fuel gas stream.

[0060] In one aspect of the present invention, the first fuel gas supply line, the second fuel gas supply line and the oxidant gas supply line are arranged in a co-annular configuration, with the oxidant gas supply line being the outermost supply line.

[0061] In one aspect of the invention, the first and second fuel gas supply lines are fixed to an upper support of the burner, said upper support being arranged to support the supply lines.

[0062] In one aspect of the invention, the burner assembly includes a burner tip for discharging first and second fuel gases into the combustion chamber, and the first and second fuel gas supply lines are fluidly connected to the burner tip.

[0063] In one aspect of the invention, the burner tip includes at least one first opening, said first opening being connected to a first fuel gas supply line for discharging a first fuel gas into the combustion chamber.

[0064] In one aspect of the invention, the burner tip includes at least one second opening, said second opening being connected to a second fuel gas supply line for discharging a second fuel gas into the combustion chamber.

[0065] In one aspect of the invention, the burner assembly includes a thermal protector, such as a burner tile, disposed around the supply line, said thermal protector configured to protect said line from external heat.

[0066] In one aspect of the invention, the burner assembly includes a first flow rate control device arranged to control a first flow rate of a first fuel gas stream and a second flow rate control device arranged to control a second flow rate of a second fuel gas stream.

[0067] In one aspect of the invention, a first flow rate control device is fluidly connected to a first fuel gas supply line and a second flow rate control device is fluidly connected to a second fuel gas supply line.

[0068] The present invention also relates to a furnace for producing a synthesis gas product, including hydrogen, by endothermic reaction of a feedstock comprising one or more burner assemblies as disclosed above.

[0069] The present invention also relates to the use of a burner assembly as disclosed above for producing a synthesis gas product by endothermic reaction of a feedstock, particularly a synthesis gas product comprising hydrogen. In particular, the present invention relates to the use of a burner assembly as disclosed above for producing a synthesis gas product comprising hydrogen by endothermic reaction of decomposing an ammonia feedstock.

[0070] Further features, details and advantages of the invention will become more apparent upon reading the description given below and with reference to the drawings. [Brief explanation of the drawings]

[0071] [Figure 1] FIG. 1 is a schematic diagram of the method of the present invention. [Figure 2] FIG. 2 is a schematic diagram of a burner assembly according to the first embodiment. [Figure 3] FIG. 3 is a schematic diagram of a burner assembly according to a second embodiment. [Figure 4] FIG. 4 is a cross-sectional view of a burner assembly according to a second embodiment. [Figure 5] FIG. 5 is a diagram focusing on the first and second supply lines according to the embodiment of FIGS. [Figure 6] FIG. 6 is a schematic diagram of a furnace of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0072] 1 illustrates a process 100 for producing a synthesis gas product comprising hydrogen by the endothermic decomposition of an ammonia feed stream. In this specific embodiment, where the synthesis gas product is the product of the endothermic decomposition of ammonia, "synthesis gas product" refers to a cracked gas product comprising hydrogen and nitrogen. However, it should be noted that the present invention encompasses all types of endothermic reactions, such as steam methane reforming. Thus, "synthesis gas product" refers to a gas product synthesized by a chemical reaction carried out in any endothermic process, such as steam methane reforming, ammonia cracking, or methanol cracking.

[0073] The method comprises the following steps: - providing an ammonia feedstock comprising ammonia; - supplying 104 a first fuel gas containing at least 20% ammonia to the combustion chamber at a first flow rate; - supplying 105 a first portion of a second fuel gas to the combustion chamber at a second flow rate, said second fuel gas comprising at least 10% hydrogen, wherein the first portion of the second fuel gas is delivered to the combustion chamber separately from the first fuel gas; - supplying combustion air 106; - combustion 107 of the supplied first fuel gas and the supplied second fuel gas together with combustion air in a combustion chamber to provide heat 108 for the endothermic reaction 103; Includes:

[0074] In this way, combustion is optimized, and in fact the first fuel gas, the second fuel gas and the combustion air can be properly mixed at the gas tip outlet, and the mixing is therefore optimized in the combustion chamber, so that the generated flame is more stable.

[0075] The first and second fuel gases and the combustion air gas are mixed in the combustion chamber to obtain a combustion mixture 107. Combustion 107 is performed by igniting the combustion mixture.

[0076] The method also includes controlling the first and second fuel gas flow rates 111. Such controlling can avoid flame instabilities due to changes in the first fuel / second fuel, i.e., ammonia / hydrogen, ratio.

[0077] As an alternative or in addition to step 111 of controlling the first flow rate and the second flow rate, the method includes supplying a second portion of a second fuel gas along with the first fuel gas, wherein the second portion of the second fuel gas is mixed with the first fuel gas.

[0078] Supplying the second portion of the second fuel gas along with the first fuel gas is controlled so that the mixing portion of the second fuel gas in the first fuel gas is comprised between 5% and 35%, preferably between 10% and 20%.

[0079] The second fuel gas delivers the hydrogen-rich fuel gas to the combustion chamber. In a preferred embodiment, the second fuel gas is injected into the first fuel gas to deliver the hydrogen-rich fuel gas into the first fuel gas.

[0080] This method ensures better flame stabilization during combustion, and the second fuel gas contains flame stabilizing hydrogen.

[0081] The method also comprises the steps of: providing an ammonia feed stream 101; conditioning 102 the ammonia feed stream; Releasing syngas products109; and Processing the synthesis gas product 110; Includes:

[0082] Here, conditioning step 102 may be, for example but not limited to, vaporizing an ammonia feed stream.

[0083] This decomposition reaction of the ammonia feed stream is an endothermic reaction that requires heat and is carried out in the presence of an active catalyst that promotes the decomposition reaction of the ammonia feed stream when heat is provided to the endothermic decomposition reaction.

[0084] The method includes a step 109 of releasing the synthesis gas product. During this step, the synthesis gas product is released from the unit where the endothermic decomposition reaction occurs, to be optionally processed in a processing step 110. For example, this processing step can be a purification step, using classical purification methods such as PSA, cryogenic separation, membrane, TSA, etc. Purified hydrogen is thus obtained.

[0085] FIG. 2 shows a burner assembly 1 according to a first embodiment. Here, the burner assembly 1 includes a combustion air supply line 3 surrounding a first fuel gas supply line 5 and a second fuel gas supply line 8. The first fuel gas contains at least 20% ammonia, and the second fuel gas contains at least 10% hydrogen. The first fuel gas supply line 5 and the second fuel gas supply line 8 are adjacent and form an inner tube 11. They are separated by a liquid-tight layer 10. The combustion air supply line 3, the first fuel gas supply line 5, and the second air supply line 8 are arranged to separately deliver combustion air, the first fuel gas, and the second fuel gas to a combustion chamber 7, where combustion of the first and second fuel gases takes place. The burner assembly 1 includes a flame holder 6 arranged to generate a flame within the combustion chamber 7.

[0086] The fuel gas supply lines include a fuel gas mixing control device positioned to mix a portion of one of the fuel gas streams with the other fuel gas stream in one of the first or second fuel gas supply lines.

[0087] The first and second fuel gases exit the first and second fuel gas supply lines 5 and 8 through burner tips 9 containing openings, each of which is sized to meet the optimum velocity requirements for a particular combustion of a different fuel gas before discharging them into the combustion chamber 7, and the flow of hydrogen contained in the second fuel gas is controlled to mix a portion of the hydrogen-containing fuel gas with the ammonia contained in the first fuel gas depending on the availability, amount, and flow ratio of the two fuel gases.

[0088] The first fuel supply line 5 , the second fuel supply line 8 and the combustion air supply line 3 are arranged within the casing 1 .

[0089] The burner assembly includes a thermal protector 4, e.g. a burner tile, arranged around the supply lines 3, 5, 8, said thermal protector being configured to protect said lines from external heat.

[0090] The first and second fuel gas velocities can be controlled by flow control devices for each fuel gas. A first flow control device 12 for the first fuel gas is fluidly connected to the first fuel gas supply line 5, and a second flow control device 13 for the second fuel gas is fluidly connected to the second fuel gas supply line 8.

[0091] 3 is a schematic diagram of a burner assembly 21 according to a second embodiment. Here, the burner assembly 21 includes a combustion air supply line 23 surrounding a first fuel gas supply line 25, which in turn surrounds a second fuel gas supply line 28. The first and second fuel gas supply lines 25 and 28 form an inner tube 31 with a surrounding layer 30 forming another tube, which in turn forms the second fuel gas supply line 28. The layer 30 is liquid-tight. In other words, the combustion air supply line 23, the first fuel gas supply line 25, and the second air supply line 28 are arranged in a co-annular configuration. The combustion air supply line 23, the first fuel gas supply line 25, and the second fuel gas supply line 28 are arranged to separately deliver combustion air, the first fuel gas, and the second fuel gas to a combustion chamber 27, where combustion of the first and second fuel gases takes place. Burner assembly 21 includes a flame holder 26 positioned to generate a flame within a combustion chamber 27 .

[0092] The fuel gas supply lines include a fuel gas mixing control device positioned to mix a portion of one of the fuel gas streams with the other fuel gas stream in one of the first or second fuel gas supply lines.

[0093] The first and second fuel gases exit first and second fuel gas supply lines 25 and 28 through burner tips 29 containing openings, each of which is sized to meet the optimum velocity requirements for combustion specific to a different fuel gas before discharging them into combustion chamber 27, and the flow of hydrogen contained in the second fuel gas is controlled to mix a portion of the hydrogen-containing fuel gas with the ammonia contained in the first fuel gas depending on the availability, amount, and flow ratio of the two fuel gases.

[0094] The first fuel supply line 25 , the second fuel supply line 28 , and the combustion air supply line 23 are arranged within the casing 21 .

[0095] The burner assembly includes thermal protection 24, such as a burner tile, disposed around the supply lines 23, 25, 28, said thermal protection being configured to protect said lines from external heat.

[0096] The first and second fuel gas velocities can be controlled by flow control devices for each fuel gas. A first flow control device 32 for the first fuel gas is fluidly connected to the first fuel gas supply line 25, and a second flow control device 33 for the second fuel gas is fluidly connected to the second fuel gas supply line 28.

[0097] Figure 4 is a cross-sectional view of the burner assembly of Figure 3. The combustion air supply line has a third flow cross-section 40. The first fuel gas supply line has a first flow cross-section 41. The second fuel gas supply line has a second flow cross-section 42. The third cross-section 40 surrounds the first flow cross-section 41, and the first flow cross-section 41 surrounds the second flow cross-section 42. In other words, the combustion air supply line, the first fuel gas supply line, and the second fuel gas supply line are arranged co-annularly. The casing 22 surrounds the third cross-sections.

[0098] FIG. 5 shows the first and second fuel supply lines of the burner assembly of FIG.

[0099] Burner tip 29 includes openings 35 and 36. First opening 35 is connected only to first fuel supply line 25, while second opening 36 is connected to second fuel supply line 28. Each of the burner tip openings is sized to meet the optimum velocity requirements for specific combustion of different fuel gases before discharging them into the combustion chamber. The flow of hydrogen contained in the second fuel gas is controlled to mix a portion of the hydrogen-containing fuel gas with the ammonia contained in the first fuel gas depending on the availability, amount, and flow ratio of the two fuel gases. In this embodiment, the first opening is ring-shaped.

[0100] FIG. 6 shows a furnace 200 including multiple burner assemblies such as those disclosed in FIGS.

[0101] Furnace 200 includes multiple reactors 201 configured to produce a synthesis gas product, here including hydrogen, by endothermic decomposition of an ammonia feed stream. Reactors 201 are fluidly arranged parallel to one another.

[0102] The furnace 200 includes a plurality of burner assemblies 202, as previously disclosed, configured to generate a flame to heat the unit 201. The burner assemblies 202 here include a first fuel supply line 205 arranged to deliver a first fuel gas to the combustion chamber, said first fuel supply line surrounding a second fuel supply line 206 arranged to deliver at least a portion of a second fuel gas to the combustion chamber.

[0103] Combustion takes place in a combustion chamber, said combustion being arranged to generate heat and provide said heat to reactor 201 .

Claims

1. 1. A method (100) for producing a synthesis gas product by endothermic reaction of a feedstock, comprising the steps of: - supplying (104) a first fuel gas containing at least 20% ammonia to the combustion chamber at a first flow rate; - supplying (105) a second fuel gas comprising at least 10% hydrogen to the combustion chamber at a second flow rate, wherein at least a first portion of one of the fuel gases is delivered to the combustion chamber separately from the other fuel gas; - providing an oxidizing gas flow (106); - combustion (107) of said supplied first fuel gas and said supplied second fuel gas together with said supplied oxidizing gas stream in said combustion chamber to provide (108) heat for said endothermic reaction (103); A method (100) comprising:

2. 10. The method (100) of claim 1, wherein the feedstock is an ammonia feedstock and the endothermic reaction is an endothermic decomposition reaction of the ammonia feedstock.

3. 3. The method (100) of claim 1 or 2, wherein the first and second fuel gases and the oxidizing gas are mixed in the combustion chamber to obtain a combustion mixture.

4. The method (100) of any one of claims 1 to 3, wherein the method comprises controlling (111) the first flow rate of the first fuel gas and the second flow rate of the second fuel gas.

5. 5. The method (100) of any one of claims 1 to 4, wherein the method comprises the step of supplying a second portion of one of the fuel gases, e.g., the second fuel gas, along with the other fuel gas, e.g., the first fuel gas, and wherein the second portion of the fuel gas, e.g., the second gas, is mixed with the other fuel gas, e.g., the first fuel gas.

6. 6. The method (100) of any one of claims 1 to 5, wherein the step (105) of supplying the second fuel gas comprises separately delivering at least a first portion of the second fuel gas from the first fuel gas to the combustion chamber.

7. A burner assembly (1, 21) for injecting heat into an endothermic reactor, comprising: at least one oxidizing gas supply line (3, 23) configured to deliver a flow of oxidizing gas to the combustion chamber of said furnace; a fuel gas supply line (5, 8, 25, 28) configured to deliver a fuel gas to be combusted together with said oxidizing gas in said combustion chamber (7, 27), in which: a first fuel gas supply line (5, 25) configured to deliver a first fuel gas flow to said combustion chamber (7, 27); a second fuel gas supply line (8, 28) configured to deliver a second fuel gas stream to the combustion chamber (7, 27), the second fuel gas supply line (8, 28) configured to deliver the second fuel gas stream to the combustion chamber (7, 27) separately from the first fuel gas stream; a fuel gas mixing control device arranged to mix a portion of one of the fuel gas streams with the other fuel gas stream in one of the first or second fuel gas supply lines;

8. 8. A burner assembly (1, 21) according to claim 7, wherein the first fuel gas supply line (5, 25) has a first flow cross section (14, 41) and the second fuel gas supply line (8, 28) has a second flow cross section (15, 42).

9. 9. A burner assembly (1, 21) according to any one of claims 7 or 8, wherein the first fuel gas supply line (5, 25) and the second fuel gas supply line (8, 28) are separated by a liquid-tight layer (10, 30).

10. A burner assembly (1, 21) according to any one of claims 7 to 9, wherein the first fuel gas supply line (25) and the second fuel gas supply line (28) are arranged co-annularly.

11. A burner assembly (1, 21) according to any one of claims 7 to 10, wherein the oxidizing gas supply line (3, 23) is arranged co-annularly with the first and second fuel gas stream supply lines (5, 8, 25, 28).

12. 12. The burner assembly (1, 21) according to any one of claims 7 to 11, wherein the burner assembly (1, 21) comprises a burner tip (9, 29) for discharging the first and second fuel gases into the combustion chamber (7, 27), and the first fuel gas supply line (5, 25) and the second fuel gas supply line (8, 28) are fluidly connected to the burner tip (9, 29).

13. A burner assembly (1, 21) according to any one of claims 7 to 12, wherein the burner tip (9, 29) includes at least one first opening (35), said first opening being connected to said first fuel gas supply line (5, 25) for discharging said first fuel gas into said combustion chamber (7, 27).

14. A burner assembly (1, 21) according to any one of claims 7 to 13, wherein the burner tip (9, 29) includes at least one second opening (36), the second opening (36) being connected to the second fuel gas supply line (8, 28) for discharging the second fuel gas into the combustion chamber (7, 27).

15. A burner assembly (1, 21) according to any one of claims 7 to 14, wherein the burner assembly comprises a first flow rate control device (12, 32) arranged to control a first flow rate of the first fuel gas flow, and a second flow rate control device (13, 33) arranged to control a second flow rate of the second fuel gas flow.

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