Method and system for producing a gas comprising nitrogen (N2) and hydrogen (H2) by combustion of hydrogen in the presence of air

Abstract

The technology relates to a method and a system for producing a gas comprising nitrogen (N2) and hydrogen (H2) in a reaction chamber of length L of a reactor. The method comprises the injection of air and the injection of hydrogen into the reactor and the combustion of a portion of the injected hydrogen with the oxygen from the air in the reaction chamber, in the presence of a molar superstoichiometric excess of hydrogen relative to the oxygen from the air. The combustion is maintained by a flame produced by a flow of air having a velocity v1 resulting from the injection of air, surrounded by a flow of hydrogen having a velocity v2 resulting from the injection of hydrogen, with a velocity v2 which is greater than v1.

Description

[0001] METHOD AND SYSTEM FOR PRODUCING A GAS COMPRISING NITROGEN (N2) AND HYDROGEN (H2) BY COMBUSTION OF HYDROGEN

[0002] IN THE PRESENCE OF AIR

[0003] TECHNICAL FIELD

[0004] The present application relates to a method and a system for producing a gas comprising nitrogen (N2) and hydrogen (H2) by combustion of hydrogen in the presence of air. More particularly, the method and the system can be used to produce a synthesis gas based on N2 and H2 usable for producing ammonia.

[0005] STATE OF THE ART

[0006] Ammonia is a commodity that is central to the production of a wide range of chemicals. Furthermore, its potential use as a fuel—or energy carrier—is currently being considered. Ammonia can be produced using the well-known Haber-Bosch process, which is based on the following reaction:

[0007] (1 ) N2+ 3H2- 2NH3

[0008] To carry out this reaction, nitrogen and hydrogen are required in a molar ratio of H2 / N2 equal to 3. The mixture of nitrogen and hydrogen required for the reaction constitutes what is called synthesis gas.

[0009] The hydrogen required to generate syngas can be produced in a variety of ways. In a sustainable development context, this hydrogen can be produced using water electrolysis systems with a renewable electricity supply (e.g., hydroelectric, wind, solar).

[0010] On the other hand, the nitrogen required to make syngas comes from air, which contains approximately 79% nitrogen and approximately 21% oxygen. Various approaches are already in use for producing nitrogen from air. Nitrogen can be produced cryogenically, by membrane separation, or by physical adsorption (Pressure Swing Adsorption or PSA).

[0011] An alternative approach to producing nitrogen is to react oxygen from the air, in the presence of hydrogen, so as to transform this oxygen into water vapor according to the reaction:

[0012] Sufficient hydrogen can be burned to completely convert the oxygen in the air into water vapor. This water vapor can then be separated, for example by condensation, to recover the nitrogen.

[0013] To produce synthesis gas for ammonia production, an electrolysis system can be used that can produce both the hydrogen required for ammonia synthesis and also the amount of hydrogen that must be burned to convert the oxygen in the air used to produce the nitrogen required for ammonia synthesis into water vapor.

[0014] However, the combustion of hydrogen in the presence of air results in the formation of nitrogen oxides (NOx), which are oxidizing molecules that can interact with the catalyst, generally iron-based, used for ammonia synthesis. The synthesis gas used to produce ammonia must therefore not contain a significant amount of NOx.

[0015] A process for producing a hydrogen and nitrogen gas, useful for example for the synthesis of ammonia, by combustion of hydrogen in the presence of air is particularly interesting. A process for producing a hydrogen and nitrogen gas, by simple combustion of hydrogen in the presence of air, which can be implemented in a reactor of simple design, while limiting the formation of NOx is attractive. Such a process will be described in the following. SUMMARY

[0016] According to a first aspect, the present technology relates to a method for producing a gas comprising nitrogen (N2) and hydrogen (H2) in a reaction chamber of length L of a reactor, comprising injecting air and injecting hydrogen into the reactor and combusting a portion of the injected hydrogen with oxygen from the air in the reaction chamber in the presence of a molar overstoichiometric excess of hydrogen relative to the oxygen from the air, wherein: the combustion is supported by a flame produced by an air flow having a velocity vi resulting from the air injection, surrounded by a hydrogen flow having a velocity V2 resulting from the hydrogen injection, with the velocity V2 being greater than vi.

[0017] According to one embodiment, the method is such that the speed vi is from about 1 m / s to about 200 m / s. According to another embodiment, the speed vi may be from about 5 m / s to about 150 m / s. The speed vi may also be from about 10 m / s to about 100 m / s.

[0018] According to another embodiment, the method is such that the speed V2 is from about 2 m / s to about 220 m / s. According to another embodiment, the speed V2 may be from about 10 m / s to about 200 m / s. The speed V2 may also be from about 15 m / s to about 175 m / s.

[0019] According to another embodiment, the method is such that the air is injected with a molar flow rate F1, the hydrogen is injected with a molar flow rate F2, and the ratio F1 / F2 is between about 1.2 and about 3.5. According to another embodiment, the ratio F2 / F1 may be between about 2 and about 3.5. The ratio F2 / F1 may also be between about 2.8 and 3.5.

[0020] According to another embodiment, the method is such that the length L of the reaction chamber is such that the volume of the reaction chamber allows a minimal residence time of the air and hydrogen, inside the reaction chamber. According to another embodiment, the residence time can be from 0.001 to 1 second. The residence time can also be from 0.01 to 0.1 second. According to another embodiment, the method is such that the reaction chamber is maintained at an average temperature T of between about 500 °C and about 1500 °C during combustion.

[0021] According to another embodiment, the method is such that the reaction chamber is maintained at a temperature Ti in a first region where the air and hydrogen streams mix in the reaction chamber, with Ti between about 600°C and about 1500°C.

[0022] According to another embodiment, the method is such that the reaction chamber is maintained at a temperature T2 in a second region near an outlet of the reaction chamber, with T2 between about 500°C and about 1500°C. The temperature T2 may also be between about 500°C and about 1200°C.

[0023] According to another embodiment, the method is such that the temperature is maintained in the reaction chamber at least in part by dissipating the heat produced by the flame to the outside of the reaction chamber.

[0024] According to another embodiment, the method is such that the temperature is maintained in the reaction chamber at least in part by recovering the heat produced by the flame, by a heat transfer fluid. The heat transfer fluid can be a liquid, an oil or a gas. The heat transfer fluid can also be water of a quality required for the generation of superheated steam. According to one embodiment, the generated steam can be recycled to provide at least part of the heat required in the process or in another process or to generate electricity. According to one embodiment, the heat dissipation can be done by convection, in the presence of air.

[0025] According to another embodiment, the method is such that the pressure in the reaction chamber is at least 1 atm. According to another embodiment, the pressure in the reaction chamber may be from 1 atm to about 10 atm. According to another embodiment, the method is such that the hydrogen comes from a water electrolysis reaction.

[0026] According to another embodiment, the method further comprises drying the gas comprising nitrogen (N2) and hydrogen (H2) produced, and recovering water. According to one embodiment, the drying may comprise condensation by cooling.

[0027] According to another aspect, the present technology relates to the use of a gas comprising nitrogen (N2) and hydrogen (H2) produced by the process as defined in the present description, for the synthesis of ammonia.

[0028] According to another aspect, the present technology relates to a system comprising at least one reactor for producing a gas comprising nitrogen (N2) and hydrogen (H2), wherein said reactor comprises: a reaction chamber comprising a wall and a first end and a second end separated by a distance L, in which the gas is produced by combustion of a portion of the injected hydrogen with oxygen from the air in the presence of a molar over-stoichiometric excess of hydrogen relative to the oxygen from the air; at least one first means for supplying the reaction chamber with an air flow at a speed vi at the first end of the chamber; at least one second means for supplying the reaction chamber with a hydrogen flow at a speed V2 at the first end of the chamber, the speed V2 being greater than vi;the first means supplying the air flow and the second means supplying the hydrogen flow are arranged so that the air flow is surrounded by the hydrogen flow during combustion.;

[0029] According to one embodiment, the system is such that the speed vi is from about 1 m / s to about 200 m / s. According to another embodiment, the speed vi may be from about 5 m / s to about 150 m / s. The speed vi may also be from about 20 m / s to about 100 m / s. According to another embodiment, the system is such that the speed V2 is from about 2 m / s to about 220 m / s. According to another embodiment, the speed V2 is from about 10 m / s to about 200 m / s. The speed V2 may also be from about 30 m / s to about 175 m / s.

[0030] According to another embodiment, the system is such that the air is supplied with a molar flow rate Fi, the hydrogen is supplied with a molar flow rate F2 and the ratio F2 / F1 is between about 1.2 and about 3.5. According to another embodiment, the ratio F2 / F1 may be between about 2 and about 3.5. The ratio F2 / F1 may also be between about 2.8 and about 3.5.

[0031] According to another embodiment, the system is such that length L of the reaction chamber is such that the volume of the reaction chamber allows a minimal residence time of air and hydrogen, inside the reaction chamber. According to another embodiment, the residence time is from 0.001 to 1 second. The residence time can also be from 0.01 to 0.1 second.

[0032] According to another embodiment, the system is configured to maintain the reaction chamber at an average temperature T of between about 500°C and about 1500°C during combustion.

[0033] According to another embodiment, the system is configured to maintain a temperature T1 of between about 600°C and about 1500°C in a first region of the reaction chamber where the gas streams mix.

[0034] According to another embodiment, the system is configured to maintain a temperature T2 of between about 500°C and about 1500°C in a second region proximate an outlet of the reaction chamber. According to another embodiment, the temperature Ï2 is between about 500°C and about 1200°C.

[0035] According to another embodiment, the system is such that the wall of the reaction chamber comprises a non-thermally insulating material to allow the temperature in the reaction chamber to be maintained at least in part by dissipating the heat produced by the combustion to the outside of the reaction chamber. According to another embodiment, the non-thermally insulating material is a metallic material.

[0036] According to another embodiment, the system further comprises a device in which a heat transfer fluid circulates to recover the dissipated heat. According to another embodiment, the heat transfer fluid is a liquid, an oil or a gas. According to another embodiment, the heat transfer fluid is water of a quality required for the generation of superheated steam. According to another embodiment, the generated steam is recycled to provide at least part of the heat required in the process or in another process or to generate electricity. According to another embodiment, the heat dissipation is done by convection, in the presence of air.

[0037] According to another embodiment, the system is such that the pressure in the reaction chamber is at least 1 atm. According to another embodiment, the pressure in the reaction chamber is from 1 atm to about 10 atm.

[0038] According to another embodiment, the system is such that the first means for supplying the air flow comprises a tube having an outer diameter and an outer wall, the air flowing through the tube from a first end to a second end.

[0039] According to another embodiment, the system is such that the second end of the tube through which the air flow enters the reaction chamber is located at the first end of the reaction chamber.

[0040] According to another embodiment, the system is such that the second means for supplying the hydrogen flow comprises a space delimited by the external diameter of the air flow supply tube and extending perpendicularly from the external wall of the tube to the internal wall of the reaction chamber.

[0041] According to another embodiment, the system is such that the reaction chamber is cylindrical in shape and the second means for supplying the hydrogen flow comprises an annular space delimited by the external diameter of the air flow supply tube and extending perpendicularly from the external wall of the tube to the internal wall of the reaction chamber.

[0042] According to another embodiment, the system is such that: the first means for supplying the air flow comprises a first tube having an outer diameter and an outer wall, the air flowing through the first tube from a first end of the first tube to a second end of the first tube, and the second means for supplying the hydrogen flow comprises a second tube having an inner diameter and an inner wall, the hydrogen flowing through the second tube from a first end of the second tube to a second end of the second tube.

[0043] According to another embodiment, the system is such that the second end of the first tube through which air enters the reaction chamber and the second end of the second tube through which hydrogen enters the reaction chamber are both located at the first end of the reaction chamber.

[0044] According to another embodiment, the system is such that the hydrogen flow is supplied into the reaction chamber through a space delimited by the external diameter of the first tube and extending perpendicularly from the external wall of the first tube to the internal wall of the second tube.

[0045] According to another embodiment, the system is such that the reaction chamber is cylindrical in shape and the hydrogen flow is supplied into the reaction chamber through an annular space delimited by the external diameter of the first tube and extending perpendicularly from the external wall of the first tube to the internal wall of the second tube.

[0046] According to another embodiment, the system is such that the hydrogen comes from an electrolysis reaction of water.

[0047] According to another embodiment, the system further comprises a device for drying the gas comprising the nitrogen (N2) and hydrogen (H2) produced and for recovering water. According to another embodiment, the device for drying and recovering water comprises a cooling condensation apparatus.

[0048] BRIEF DESCRIPTION OF THE FIGURES

[0049] Figure 1 represents a schematic sectional view along the vertical of a reactor which can be used to carry out the process according to one embodiment.

[0050] Figure 2 represents a schematic sectional view along the vertical of a reactor which can be used to carry out the process according to another embodiment.

[0051] Figure 3 represents a schematic view in section along the vertical of a system comprising several reactors according to Figure 1 which can be used to carry out the process according to another embodiment.

[0052] Figure 4 represents a schematic view in section along the vertical of a system comprising several reactors according to Figure 2 which can be used to carry out the process according to another embodiment.

[0053] Figure 5 represents a schematic sectional view along the vertical of a reactor which can be used to carry out the process according to yet another embodiment.

[0054] DETAILED DESCRIPTION

[0055] All technical and scientific terms and expressions used herein have the same meaning as generally understood by a person skilled in the art of the present technology. Definitions of certain terms and expressions used are nevertheless provided below.

[0056] The term "about" as used in this document means approximately, in the region of, and around. When the term "about" is used in connection with a numerical value, it modifies it, for example, above and below by a variation of 10% from the nominal value. This term may also take into account, for example, the experimental error of a measuring device or the rounding of a value.

[0057] Where a range of values ​​is referred to in this application, the lower and upper bounds of the range are, unless otherwise indicated, always included in the definition. Thus, where a range of values ​​is indicated as "between X and Y" or "between about X and about Y", the values ​​X and Y are included in the definition.

[0058] In this disclosure, the term "synthesis gas" is used to identify a gas mixture comprising at least hydrogen (H2O) and nitrogen (N2). In some embodiments, the synthesis gas may comprise water vapor (H2O).

[0059] The term "stream" is used to describe the different gas streams that are used to carry out the synthesis gas production reaction inside the reaction chamber. As will be described in more detail below, the reaction involves a stream containing hydrogen (H2) and an air stream containing oxygen (O2) and nitrogen (N2) that will react with each other to form a synthesis gas.

[0060] This document therefore presents an innovative method and system for producing a gas comprising nitrogen (N2) and hydrogen (H2) in a reaction chamber of a reactor. The method comprises injecting air and injecting hydrogen into the reactor and combusting a portion of the injected hydrogen with oxygen from the air in the reaction chamber. The reaction takes place in the presence of a molar over-stoichiometric excess of hydrogen relative to the oxygen from the air. Combustion in the reaction chamber is supported by a flame produced by an air flow having a velocity vi resulting from the air injection, surrounded by a hydrogen flow having a velocity V2 resulting from the hydrogen injection, with the velocity V2 being greater than the velocity vi.

[0061] The reaction to form the gas is therefore carried out in the presence of a molar superstoichiometric excess of hydrogen relative to the oxygen in the air. By "molar superstoichiometric excess of hydrogen", it will be understood that the quantity of hydrogen (hte) injected into the reactor must be sufficient to, on the one hand, allow the combustion reaction with the oxygen in the air according to equation (2) by consuming all the injected oxygen, and on the other hand to allow a portion of the injected hydrogen not to be burned and to be able to end up in the synthesis gas produced. Thus, a molar superstoichiometric excess of hydrogen relative to oxygen implies a molar ratio Fte to O2 necessarily greater than 2, preferably at least 5.8. According to certain embodiments, the molar ratio H2 to O2 is at most 16.7.

[0062] The combustion of hydrogen in the presence of the super-stoichiometric excess of hydrogen is therefore carried out with a flame which is produced by the air flow surrounded by the hydrogen flow, in the reaction chamber. The combustion can be initiated using an ignition device, such as an electric arc, an incandescent wire, a candle, or any other known energy source. In the reaction chamber, the air flow, and therefore the flame, is therefore in a sort of envelope formed by the hydrogen flow. This hydrogen envelope around the air flow can be formed thanks to i) the difference in speed of the air and hydrogen flows entering the reaction chamber, the speed V2 of the hydrogen flow being greater than the speed vi of the air flow, and ii) the geometry of the entry of the gases, i.e. air and hydrogen, into the reaction chamber.

[0063] A more detailed description of certain particular embodiments of the method and of the system in which it can be implemented will now be provided with reference to the figures.

[0064] Figure 1 shows the general operating principle of a reactor that can be used to produce hydrogen and nitrogen-based synthesis gas according to certain embodiments. The reactor may comprise at least one reaction chamber of length L provided with a wall, at least one first air supply means and at least one second hydrogen supply means. The first and second means for supplying the reaction chamber with the air flow and the hydrogen flow are located at a first end of the chamber, which, in Figure 1, is located at the bottom of the reaction chamber. Furthermore, the means for supplying the hydrogen and air flows are arranged to allow the air flow to be surrounded by the hydrogen flow during combustion, i.e. so that the hydrogen flow can form an envelope around the air flow.Thus, the arrangement of the means for supplying the air and hydrogen flows makes it possible to have a central air flow with the hydrogen flow surrounding it in the reaction chamber.

[0065] In some embodiments, the first means for supplying the air flow may comprise a tube having an outer diameter and an outer wall, with air flowing through the tube from a first end to a second end. In one embodiment, the second end of the tube through which the air flow enters the reaction chamber may be located approximately at the first end of the reaction chamber. In another embodiment, the second end of the tube through which the air flow enters the reaction chamber may be located within the first third of the height of the reaction chamber from the first end of the chamber. The second means for supplying the hydrogen flow may comprise a space defined by the outer diameter of the air flow supply tube and extending perpendicularly from the outer wall of the tube to the inner wall of the reaction chamber.

[0066] According to another possible arrangement, the reaction chamber may be cylindrical in shape and the second means for supplying the hydrogen flow may comprise an annular space delimited by the external diameter of the air flow supply tube and extending perpendicularly from the external wall of the tube to the internal wall of the reaction chamber.

[0067] In one embodiment, the reactor itself may consist of two concentric tubes forming an arrangement as shown more particularly in Figure 1. In the tube arrangement shown in Figure 1, the outer tube is both forming the wall of the reaction chamber and defining the annular space through which the hydrogen stream is fed. The inner tube is used to inject air and the space extending from the outer wall of the inner tube to the inner wall of the outer tube forms the annular space for feeding the hydrogen stream. In another embodiment, the reactor itself may consist of three tubes forming an arrangement as shown more particularly in Figure 2. In this embodiment, the reactor may comprise a first tube for injecting air, a second tube for injecting H2, and finally, a third tube defining the wall of the reaction chamber.In the arrangement shown in Figure 2, hydrogen is injected into the annular space defined by the outer diameter of the air injection tube and the inner diameter of the hydrogen injection tube. As shown in Figure 2, the hydrogen injection tube terminates, in its upper part, at the lower end of the tube defining the wall of the reaction chamber. As also shown in Figure 2, the upper ends of the air injection and hydrogen injection tubes may be substantially aligned, thus the air and hydrogen streams enter the reaction chamber at the same level.

[0068] According to one embodiment, the system for producing the synthesis gas based on nitrogen and hydrogen, according to the present technology, may comprise several reactors in parallel as shown for example in Figures 3 and 4. Thus, the system may comprise an enclosure containing a multitude of reactors where each reactor, which may be of the type shown in Figure 1 or of the type shown in Figure 2, receives a flow of air and a flow of hydrogen. The air on the one hand and the hydrogen on the other hand may be supplied to the system by means of a common inlet for each gas. Each of the gases is then supplied to each reactor. The synthesis gas produced in each of the reactors may then be assembled and discharged from the system through a common outlet.

[0069] According to another embodiment, the system for producing the synthesis gas based on nitrogen and hydrogen, according to the present technology, may comprise a reactor as shown in Figure 5 designed to produce several combustion reactions of hydrogen by oxygen from the air, in the presence of a superstoichiometric excess, inside a single reaction chamber. Thus, the reactor may be arranged to receive a main air flow and a main hydrogen flow, each of the main flows separating into several secondary flows. For each combination of secondary air and hydrogen flows entering the reaction chamber, the speed vi of the secondary air flow is lower than the speed V2 of the secondary hydrogen flow. Thus, in the reaction chamber, each secondary air flow is found in a sort of envelope formed from the associated secondary hydrogen flow.The flame produced by each combination of secondary air and hydrogen streams is also enveloped by the related secondary hydrogen stream. The synthesis gas produced for each combination of secondary air and hydrogen streams can be recovered in a global synthesis gas stream at the reactor outlet.

[0070] In one embodiment, a reactor for producing syngas is designed such that the temperature in the reaction chamber of the reactor is maintained at a certain level to limit the production of NOx. Thus, in some embodiments, the system is designed to maintain the reaction chamber at an average temperature T of between about 500°C and about 1500°C during combustion. The average temperature T in the reaction chamber during combustion may, for example, be maintained at about 500°C, 600°C, 700°C, 800°C, 900°C, 1000°C, 1100°C, 1200°C, 1300°C, 1400°C or 1500°C or may be any value in between. In addition, it is possible in some embodiments to control the temperature in the regions at the ends of the reaction chamber to maintain a certain temperature therein.For example, the system may be configured to maintain a temperature Ti in a region near the inlet of the reaction chamber where the gas streams mix, of between about 600°C and about 1500°C. The temperature Ti may therefore be maintained at about 600°C, 700°C, 800°C, 900°C, 1000°C, 1100°C, 1200°C, 1300°C, 1400°C or 1500°C or at any value between these temperatures. In other embodiments, the system may be configured to maintain a temperature Ï2 in a region near the outlet of the reaction chamber of between about 500°C and about 1500°C. In some cases, the temperature Ï2 in the region near the outlet of the reaction chamber can be controlled to be between about 500°C and about 1200°C.The temperature T2 can therefore be maintained at approximately 500 °C, 600 °C, 700 °C, 800 °C, 900 °C, 1000 °C, 1100 °C, 1200 °C, 1300 °C, 1400 °C or 1500 °C or anywhere in between. Temperature control can be carried out in a variety of ways and more details on this will be provided below. It should also be noted that the temperature of the reaction chamber as mentioned above may vary depending on the exact location where the temperature measurement is taken. Furthermore, it should be noted that the temperature values ​​mentioned above may be different from the maximum temperature of the reaction itself which can reach temperatures above 1500 °C. In fact, the temperature at the hydrogen-oxygen flame can even reach values ​​of more than 2000 °C.

[0071] According to some embodiments, in addition to controlling and maintaining a certain temperature in the reaction chamber, it is possible to control the pressure to facilitate combustion. According to some embodiments, the pressure in the reaction chamber is controlled to be at least 1 atm. The pressure in the reaction chamber may, for example, vary between approximately 1 atm and 10 atm. Thus, the pressure may be 1 atm, 2 atm, 3 atm, 4 atm, 5 atm, 6 atm, 7 atm, 8 atm, 9 atm, 10 atm, or any pressure in between.

[0072] As mentioned previously, the air flow and the hydrogen flow must have different velocities in the reaction chamber, with the velocity of the hydrogen flow being greater than that of the air flow. In some embodiments, the air is injected into the reactor so as to constitute a central flow inside the reaction chamber at the velocity vi. This velocity vi is calculated from the volume flow rate of supplied air corrected to the temperature Ti and pressure in the reaction chamber, this flow rate being divided by the area perpendicular to the flow of the air injection tubing. According to some embodiments, the velocity vi can be from about 1 m / s to about 200 m / s. For example, the velocity vi can be from about 5 m / s to about 150 m / s or from about 10 m / s to about 100 m / s.Thus, the velocity vi of the central airflow can be 1 m / s, 5 m / s, 10 m / s, 20 m / s, 30 m / s, 40 m / s, 50 m / s, 60 m / s, 70 m / s, 80 m / s, 90 m / s, 100 m / s, 110 m / s, 120 m / s, 130 m / s, 140 m / s, 150 m / s, 160 m / s, 170 m / s, 180 m / s, 190 m / s, 200 m / s, or any velocity between these values.

[0073] In some embodiments, the speed V2 may be from about 2 m / s to about 220 m / s. For example, the speed V2 may be from about 10 m / s to about 200 m / s or from about 15 m / s to about 175 m / s. Thus, the velocity V2 of the hydrogen flow can be 2 m / s, 5 m / s, 10 m / s, 20 m / s, 30 m / s, 40 m / s, 50 m / s, 60 m / s, 70 m / s, 80 m / s, 90 m / s, 100 m / s, 110 m / s, 120 m / s, 130 m / s, 140 m / s, 150 m / s, 160 m / s, 170 m / s, 180 m / s, 190 m / s, 200 m / s, 210 m / s, 220 m / s or any velocity between these values ​​as long as it is greater than the velocity vi of the air flow.

[0074] As shown in Figure 1 and explained previously, according to one embodiment, the hydrogen can be supplied into the reactor in the space formed between the outer wall of the air supply tube and the inner wall of the reactor, this space being for example annular when the wall of the reactor is cylindrical. Thus, the hydrogen which is injected into the reaction chamber constitutes a hydrogen flow whose speed V2 must be greater than that of the air flow (vi). The speed V2 of the hydrogen flow entering the reaction chamber is calculated from the volume flow rate of injected hydrogen corrected to the temperature Ti and pressure in the reactor, this flow rate being divided by the surface area perpendicular to the flow of the space where the injected hydrogen circulates, this space being preferentially annular as explained above.

[0075] As shown in Figure 2 and explained previously, according to another embodiment, the hydrogen is supplied into the reactor by injection into the space formed between the outer wall of the air supply tube and the inner wall of the hydrogen supply tube, this space being for example annular when the wall of the hydrogen injection tube is cylindrical in shape. Thus, the hydrogen which is injected into the reaction chamber constitutes a hydrogen flow whose speed V2 must be greater than that of the air flow (vi). The speed V2 of the hydrogen flow entering the reaction chamber is calculated from the volume flow rate of injected hydrogen corrected to the temperature Ti and pressure in the reactor, this flow rate being divided by the surface area perpendicular to the flow of the space where the injected hydrogen circulates, this space being preferentially annular as explained above.

[0076] Air and hydrogen are fed into the reactor with certain molar flow rates to support the combustion reaction between hydrogen and oxygen in the air, while having a superstoichiometric excess of hydrogen. In some embodiments, air is fed into the reactor with a molar flow rate Fi and hydrogen is fed with a molar flow rate F2 and the ratio F2 / F1 is between about 1.2 and about 3.5. In another embodiment, the ratio between the molar flow rates of hydrogen and air F2 / F1 may be between about 2 and about 3 or may be between about 2.8 and about 3.5. The ratio F2 / F1 may therefore be about 1.2 or 1.5 or 2 or 2.5 or 3 or 3.5 or any ratio between these values.According to certain embodiments, the ratio F2 / F1 can be approximately 3 and more particularly approximately 2.8, which corresponds to the theoretical molar ratio for producing a synthesis gas containing the proportions of H2 and N2 required to produce ammonia according to reaction (2), while allowing the complete transformation, into H2O, of the oxygen contained in the injected air.

[0077] As previously indicated, the reaction chamber of the reactor in which the synthesis gas is produced may have a length L corresponding substantially to a distance between a region where the hydrogen stream and the air stream mix in the reaction chamber (eg, at the lower end of the chamber) and a region near the outlet of the reaction chamber at the other end of the reaction chamber (eg, at the upper end of the chamber). The length L of the reaction chamber may be such that the volume of the reaction chamber allows for a minimal residence time of the air and hydrogen, inside the reaction chamber.

[0078] According to one embodiment, the length L is such that the residence time t of the gases in the reaction chamber is from 0.001 to 1 second. According to another embodiment, the residence time is from 0.01 to 0.1 second. The residence time is defined as follows:

[0079] (3) t = V / ((Q2+QI ) * (T+273) / 298 / P) * K where V is the volume of the reaction chamber, Q2 is the standard volume flow rate (25 °C and 1 atm) of the H2 supplied, Qi is the standard volume flow rate (25 °C and 1 atm) of the air supplied, T is the average temperature (°C) in the reaction chamber and finally, P is the pressure (atm) inside the reactor. Finally, K is a constant of units. For each of the air and hydrogen flows, the relationship between the molar flow rate and the standard volume flow rate is defined, respectively for air and hydrogen, by the following equations:

[0080] (4) Qi=Fi * R * (T+273) / P and (5) Q2=F2 * R * (T+273) / P where R is the gas constant.

[0081] Thus, the residence time t in the reaction chamber may be from 0.001 to 1 second. In another embodiment, the residence time t may be from 0.01 to 0.1 second. The residence time t may therefore be 0.001 or 0.002 or 0.005 or 0.01 or 0.015 or 0.02 or 0.03 or 0.04 or 0.05 or 0.06 or 0.07 or 0.08 or 0.09 or 0.1 or 0.2 or 0.3 or 0.4 or 0.5 or 0.6 or 0.7 or 0.8 or 0.9 or 1 second, or any time between these values.

[0082] According to certain embodiments, without however being limited to these values, the length L of the reaction chamber can be between 0.10 m and 3 m approximately. The length L can be determined to achieve a capacity of the system to maintain a desired conversion efficiency.

[0083] As mentioned above, the temperature in the reaction chamber can be maintained at a certain value between a minimum temperature and a maximum temperature during combustion and synthesis gas production. By maintaining a certain temperature in the reaction chamber, it is thus possible to limit the production of NOx. One way to control the temperature to remain at a certain value is to carry out the combustion in a reaction chamber whose wall is made of a thermally non-insulating material. Thus, the heat released by the combustion of hydrogen by the oxygen in the air in the reaction chamber can, at least in part, be dissipated through the non-insulating material of the wall to the outside of the reaction chamber (see Figure 1). Such a thermally non-insulating material can be, for example, a metallic material such as a metal alloy. The material is also preferably corrosion-resistant.For example, a metal such as Inconel® or another equivalent material can be used to form the wall of the reaction chamber.

[0084] In some embodiments, the heat released by combustion through the wall of the reaction chamber may be dissipated by convection, in the presence of air. Thus, it is possible to circulate air around the reactor continuously during combustion to maintain a certain temperature in the reaction chamber. In other embodiments, the heat that is dissipated through the wall of the reaction chamber may be recovered by a device in which a heat transfer fluid circulates. A heat exchange device in which the heat transfer fluid is a liquid, an oil or a gas may be used. Such a device may, for example, comprise a jacket surrounding the reactor, in which the heat transfer fluid circulates. In one embodiment, the heat dissipated through the wall of the reaction chamber may be used to heat water circulating in a device surrounding the chamber so as to generate water vapor.Recovering the heat released by the reactor can be particularly advantageous for generating superheated steam with water of appropriate quality circulating in the heat exchange device. Furthermore, in certain embodiments, the steam thus generated can be recycled to provide at least part of the heat required in the process, in another process or to generate electricity. For example, the superheated steam produced can be used to power a steam turbine used for the production of electricity. The synthesis gas produced by the system described above and which leaves the reactor therefore comprises nitrogen (N2) and hydrogen (H2), and also a certain content of water vapor. The gas leaving the reactor is therefore a wet raw gas which can then be dried to recover a dry gas. The raw gas can be dried by known means of water vapor separation.In some embodiments, the raw gas drying and water recovery device may comprise a cooling condensation apparatus. It is also possible, if necessary, to use other means of water vapor separation such as, for example, an adsorption drying medium. The water that is recovered during the drying of the raw synthesis gas may then be reused in the process, as will be explained below, for example to produce the hydrogen that will be fed into the reactor.

[0085] In a context of sustainable development, it is proposed that the hydrogen used for the production of syngas be produced by a water electrolysis system with a renewable source of electricity (hydraulic, wind, or solar). In a particular embodiment, the water electrolysis system may use electricity produced, at least in part, from superheated water vapor obtained by recovering the heat released by the reactor as mentioned above. In addition, the water used to obtain hydrogen by water electrolysis may come, at least in part, from the water recovered during the drying of the syngas at the outlet of the reactor, as detailed above. Alternatively, the water recovered during the drying of the syngas may be used, at least in part, as a heat transfer fluid in the device for recovering the heat released by the reactor as explained previously.

[0086] The synthesis gas obtained by the present technology, which comprises nitrogen and hydrogen, can be used in various industrial processes for which these two gases are required. Even if such an industrial process preferably comprises the production of ammonia, other industrial processes using H2 / N2 mixtures with molar ratios different from that required for the synthesis of ammonia can also use the synthesis gas produced by the present technology. To obtain a synthesis gas intended to be used in the production of ammonia, the ratio between the molar flow rate of injected hydrogen and the molar flow rate of injected air can preferably be between 2.8 and 3.5, more particularly around 3, more particularly about 2.8.Using a ratio of 2.8 between the molar flow rate of injected hydrogen and the molar flow rate of injected air, we therefore expect to obtain, using the present technology, a synthesis gas with the following molar composition at the reactor outlet:

[0087] • N2: 22.0%

[0088] • H2: 66.3%

[0089] • H20: 11.7%

[0090] • NOx: trace.

[0091] It should be noted that although it is preferable to feed the reactor using an H2 / air molar ratio that can be between 2.8 and 3.5, to produce a synthesis gas that can be used directly for the production of ammonia, it is also quite possible to use an H2 / air ratio that is lower than 2.8 as long as the hydrogen is injected in over-stoichiometric excess compared to the oxygen in the air. Thus, a synthesis gas with an H2 / N2 molar ratio lower than the H2 / N2 molar ratio required for direct ammonia synthesis will be obtained, but it will be sufficient to add the necessary quantity of hydrogen (e.g., electrolytic hydrogen) to adjust the H2 / N2 ratio.

[0092] The technology described in this document has several advantages. It offers a simple and relatively inexpensive process for producing hydrogen and nitrogen-based synthesis gas, including a synthesis gas that can be used to synthesize ammonia. The production of synthesis gas according to the present technology is therefore conducive to a "green" ammonia production process, i.e., ammonia production with a life cycle without - or practically without - greenhouse gas (GHG) emissions. EXAMPLE

[0093] A small reactor was fabricated to define an arrangement as shown in Figure 2. This reactor was constructed from Inconel 600™ tubes. For each of the tubes, the following dimensions are given:

[0094] • Air injection tube: OD = 6.39 mm, Dl = 4.12 mm

[0095] • Fte injection tube: DE = 12.7 mm, Dl = 8.75 mm

[0096] • External tube: OD = 19.05 mm, Dl = 13.71 mm with Dl = internal diameter and OD = external diameter.

[0097] The outer tube defines the wall of the reactor's reaction chamber, with a length L = 347 mm. Based on the inner diameter of the outer tube and this length L, this gives an internal volume V equal to 51.29 cm 3 .

[0098] A first thermocouple, located at a vertical distance of 32.37 mm from the nozzle, is used to measure a proximity temperature level, Ti. A second thermocouple, located near the reactor outlet, at a vertical distance of nearly 340 mm from the nozzle, is used to measure the temperature level T2. The NO content is measured directly and continuously, using an analysis device dedicated to this purpose. The part of the gas leaving the reactor and circulating inside the analyzer is at a temperature of nearly 28 °C. NO is considered representative of nitrogen oxides.

[0099] A series of tests was carried out by varying the air and H2 flow rates (Q1 and Q2 respectively). The table below presents the main results obtained for 9 tests. For these tests, the Q1 and Q2 flow rates were varied, but the Q2 / Q1 ratio was always maintained at 3.50. This made it possible to obtain a synthesis gas based on N2 and H2 for which the H2 / N2 molar ratio was equal to 3.90.

[0100] The air flow velocity vi is calculated from the perpendicular surface defined by the inner diameter of the air injection tube and from the corrected air volume flow rate at a temperature T1 and pressure in the reaction chamber. The H2 flow velocity (V2) is calculated from the surface of the annular space defined by the inner diameter of the hydrogen injection tube and the outer diameter of the air injection tube, and from the corrected H2 volume flow rate at a temperature T1 and pressure in the reaction chamber.

[0101] The residence time t in the reactor is calculated from the volume of the reaction chamber divided by the sum of the volume flow rates Q1+Q2 (which are standard flow rates at 25 °C (298 K) and 1 atm), considering an average temperature (T1+T2) / 2 and considering the pressure level P in the reactor (1 atm), according to the following equation: t = V / ((Q1 +Q2)*1000 / 60*((T 1 +T2) / 2+273) / 298 / P

[0102] Q2 Q1 Ti T2 Tmoy NO V2 V1 t

[0103] (sL / min) (sL / min) (°C) (°C) (°C) (ppm) (m / s) (m / s) (s)

[0104] 10 2.86 875 85 480 10.79 22.9 13.8 0.0947

[0105] 11 3.14 917 100 509 9.78 26.1 15.7 0.0830

[0106] 12 3.42 956 117 537 9.96 29.4 17.6 0.0735

[0107] 13 3.71 992 135 564 9.02 32.8 19.7 0.0656

[0108] 14 4 1035 151 593 11.21 36.5 21.9 0.0588

[0109] 15 4.29 1076 169 623 10.69 40.3 24.3 0.0531

[0110] 16 4.57 1109 185 647 10.75 44.1 26.5 0.0485

[0111] 17 4.86 1135 201 668 11.3 47.7 28.7 0.0446

[0112] 18 5.14 1158 217 688 11.34 51.3 30.9 0.0413

[0113] As shown in the table, the NO content of the gas obtained in each of the tests does not vary significantly. A statistical analysis gives an average value of 10.54 ppm with a confidence interval of + / - 0.61 ppm (based on the Student factor for a probability of 95%). Increasing the flow rate of the inputs (Q1 and Q2) causes the residence time to vary from 0.095 to 0.041 seconds, but this has no significant effect on the NO content of the output gas. Although certain embodiments of the technology have been described above, the technology is not limited to these embodiments alone. Several modifications could be made to any of the embodiments described above, without departing from the scope of the present technology.

Claims

DEMANDS 1- A process for producing a gas comprising nitrogen (N2) and hydrogen (H2) in a reaction chamber of length L of a reactor, comprising the injection of air and the injection of hydrogen into the reactor and the combustion of a part of the injected hydrogen with oxygen from the air in the reaction chamber in the presence of a molar overstoichiometric excess of hydrogen relative to oxygen from the air, in which: the combustion is supported by a flame produced by an airflow having a velocity vi resulting from the air injection, surrounded by a hydrogen flow having a velocity V2 resulting from the hydrogen injection, with the velocity V2 being greater than vi. 2- The method according to claim 1, wherein the speed vi is from about 1 m / s to about 200 m / s. 3- The method according to claim 1 or 2, wherein the speed vi is from about 5 m / s to about 150 m / s. 4- The method according to any one of claims 1 to 3, wherein the speed vi is from about 10 m / s to about 100 m / s. 5- The method according to any one of claims 1 to 4, wherein the speed V2 is from about 2 m / s to about 220 m / s. 6- The method according to any one of claims 1 to 5, wherein the speed V2 is from about 10 m / s to about 200 m / s. 7- The method according to any one of claims 1 to 6, wherein the speed V2 is from about 15 m / s to about 175 m / s. 8- The method according to any one of claims 1 to 7, wherein air is injected with a molar flow rate F1, hydrogen is injected with a molar flow rate F2, and the ratio F1 / F2 is between about 1.2 and about 3.

5. 9- The method according to claim 8, wherein the ratio F2 / F1 is between approximately 2 and approximately 3.

5. 10- The method according to claim 8, wherein the ratio F2 / F1 is between approximately 2.8 and 3.

5. 11- The method according to any one of claims 1 to 10, wherein the length L of the reaction chamber is such that the volume of the reaction chamber allows a minimum residence time of air and hydrogen inside the reaction chamber. 12- The method according to claim 11, wherein the residence time is from 0.001 to 1 second. 13- The method according to claims 11 or 12, wherein the residence time is from 0.01 to 0.1 seconds. 14- The process according to any one of claims 1 to 13, wherein the reaction chamber is maintained at an average temperature T between approximately 500 °C and approximately 1500 °C during combustion. 15- The process according to any one of claims 1 to 14, wherein the reaction chamber is maintained at a temperature T1 in a first region where the air and hydrogen streams mix in the reaction chamber, with T1 between about 600 °C and about 1500 °C. 16- The method according to any one of claims 1 to 15, wherein the reaction chamber is maintained at a temperature T2 in a second region close to an outlet of the reaction chamber, with T2 between about 500 °C and about 1500 °C. 17- The process according to claim 16, wherein the temperature T2 is between approximately 500 °C and approximately 1200 °C. 18- The method according to any one of claims 14 to 17, wherein the temperature is maintained in the reaction chamber at least partly by dissipating the heat produced by the flame outwards from the reaction chamber. 19- The method according to any one of claims 14 to 18, wherein the temperature is maintained in the reaction chamber at least partly by recovering the heat produced by the flame, by a heat transfer fluid. 20- The process according to claim 19, wherein the heat transfer fluid is a liquid, an oil or a gas. 21- The process according to claim 19, wherein the heat transfer fluid is water of the quality required for the generation of superheated steam. 22- The process according to claim 21, wherein the generated steam is recycled to provide at least part of the heat required in the process or in another process or to generate electricity. 23- The process according to claim 18, wherein heat dissipation is done by convection, in the presence of air. 24- The method according to any one of claims 1 to 23, wherein the pressure in the reaction chamber is at least 1 atm. 25- The process according to any one of claims 1 to 24, wherein the pressure in the reaction chamber is from 1 atm to about 10 atm. 26- The process according to any one of claims 1 to 25, wherein the hydrogen is obtained from an electrolysis reaction of water. 27- The process according to any one of claims 1 to 26, further comprising drying the gas comprising nitrogen (N2) and hydrogen (H2) produced, and recovering water. 28- The process according to claim 27, wherein the drying comprises condensation by cooling. 29- Use of a gas comprising nitrogen (N2) and hydrogen (H2) produced by the process as defined according to any one of claims 1 to 28, for the synthesis of ammonia. 30- A system comprising at least one reactor for producing a gas comprising nitrogen (N2) and hydrogen (H2), in which said reactor comprises: a reaction chamber comprising a wall and a first end and a second end separated by a distance L, in which the gas is produced by combustion of a portion of the injected hydrogen with oxygen from the air in the presence of a molar overstoichiometric excess of hydrogen relative to oxygen from the air; at least one first means for supplying the reaction chamber with an air flow at a velocity vi at the level of the first end of the chamber; at least one second means for supplying the reaction chamber with a hydrogen flow at a velocity V2 at the level of the first end of the chamber, the velocity V2 being greater than vi;The first means supplying the air flow and the second means supplying the hydrogen flow are arranged so that the air flow is surrounded by the hydrogen flow during combustion. 31- The system according to claim 30, in which the speed vi is from about 1 m / s to about 200 m / s. 32- The system according to claim 30 or 31, wherein the velocity vi is from about 5 m / s to about 150 m / s. 33- The system according to any one of claims 30 to 32, wherein the velocity vi is from about 20 m / s to about 100 m / s. 34- The system according to any one of claims 30 to 33, wherein the speed V2 is from about 2 m / s to about 220 m / s. 35- The system according to any one of claims 30 to 34, wherein the speed V2 is from about 10 m / s to about 200 m / s. 36- The system according to any one of claims 30 to 35, wherein the velocity V2 is from approximately 30 m / s to approximately 175 m / s. 37- The system according to any one of claims 30 to 36, wherein the air is supplied with a molar flow rate Fi, the hydrogen is supplied with a molar flow rate F2, and the ratio F2 / F1 is between approximately 1.2 and approximately 3.

5. 38- The system according to claim 37, wherein the ratio F2 / F1 is between approximately 2 and approximately 3.

5. 39- The system according to claim 37 or 38, wherein the ratio F2 / F1 is between approximately 2.8 and approximately 3.

5. 40- The system according to any one of claims 30 to 39, wherein the length L of the reaction chamber is such that the volume of the reaction chamber allows a minimum residence time of air and hydrogen inside the reaction chamber. 41 - The system according to claim 40, wherein the residence time is from 0.001 to 1 second. 42- The system according to claim 40 or 41, wherein the residence time is from 0.01 to 0.1 seconds. 43- The system according to any one of claims 30 to 42, wherein the system is designed to maintain the reaction chamber at an average temperature T between approximately 500 °C and approximately 1500 °C during combustion. 44- The system according to any one of claims 30 to 43, wherein the system is designed to maintain a temperature T1 between approximately 600 °C and approximately 1500 °C in a first region of the reaction chamber where the gas streams mix. 45- The system according to any one of claims 30 to 44, wherein the system is designed to maintain a temperature T2 between about 500 °C and about 1500 °C in a second region close to an outlet of the reaction chamber. 46- The system according to claim 45, in which the temperature T2 is between approximately 500 °C and approximately 1200 °C. 47- The system according to any one of claims 43 to 46, wherein the wall of the reaction chamber comprises a non-thermally insulating material to allow the temperature in the reaction chamber to be maintained at least in part by dissipating the heat produced by combustion to the outside of the reaction chamber. 48- The system according to claim 47, wherein the non-thermally insulating material is a metallic material. 49- The system according to claim 47 or 48, further comprising a device in which a heat transfer fluid circulates to recover the dissipated heat.

50. The system according to claim 49, wherein the heat transfer fluid is a liquid, an oil, or a gas.

51. The system according to claim 49, wherein the heat transfer fluid is water of the quality required for the generation of superheated steam. 52- The system according to claim 51, wherein the generated steam is recycled to provide at least part of the heat required in the process or in another process or to generate electricity. 53- The system according to claim 47, in which heat dissipation is done by convection, in the presence of air. 54- The system according to any one of claims 30 to 53, wherein the pressure in the reaction chamber is at least 1 atm. 55- The system according to any one of claims 30 to 54, wherein the pressure in the reaction chamber is from 1 atm to about 10 atm. 56- The system according to any one of claims 30 to 55, wherein the first means for supplying the airflow comprises a tube having an external diameter and an external wall, the air flowing through the tube from a first end to a second end. 57- The system according to claim 56, wherein the second end of the tube through which the airflow enters the reaction chamber is located at the level of the first end of the reaction chamber. 58- The system according to claim 56 or 57, wherein the second means for supplying the hydrogen flow comprises a space delimited by the external diameter of the air flow supply tube and extending perpendicularly from the external wall of the tube to the internal wall of the reaction chamber. 59- The system according to claim 56 or 57, wherein the reaction chamber is cylindrical in shape and the second means for supplying the hydrogen flow comprises an annular space delimited by the external diameter of the air flow supply tube and extending perpendicularly from the external wall of the tube to the internal wall of the reaction chamber. 60- The system according to any one of claims 30 to 55, wherein: the first means for supplying the airflow comprises a first tube having an external diameter and an external wall, the air flowing through the first tube from a first end of the first tube to a second end of the first tube, and The second means for supplying the hydrogen flow comprises a second tube having an internal diameter and an internal wall, the hydrogen flowing through the second tube from one end of the second tube to a second end of the second tube. 61- The system according to claim 60, wherein the second end of the first tube through which air enters the reaction chamber and the second end of the second tube through which hydrogen enters the reaction chamber are both located at the first end of the reaction chamber. 62- The system according to claim 60 or 61, wherein the hydrogen flow is supplied into the reaction chamber through a space delimited by the external diameter of the first tube and extending perpendicularly from the external wall of the first tube to the internal wall of the second tube. 63- The system according to claim 60 or 61, wherein the reaction chamber is cylindrical in shape and the hydrogen flow is supplied into the reaction chamber through an annular space delimited by the external diameter of the first tube and extending perpendicularly from the external wall of the first tube to the internal wall of the second tube. 64- The system according to any one of claims 30 to 63, wherein the hydrogen is obtained from an electrolysis reaction of water. 65- The system according to any one of claims 30 to 64, further comprising a device for drying the gas comprising the nitrogen (N2) and hydrogen (H2) produced and for recovering water. 66- The system according to claim 65, wherein the drying and water recovery device comprises a cooling condensation apparatus.

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