Systems and methods for generating thermal energy using metal powder as a fuel

Abstract

The present invention relates to a system (S1) for generating thermal energy from the combustion of metal particles, comprising a metal particle burner in a combustion chamber (4), means (100) for injecting metal particles into the burner means, means (5, 6) for introducing air to form a premixture of air and the metal particles, means for capturing oxidized particles in the exhaust gases, either downstream of or associated with the first heat exchange means, and a heat exchanger (7) for exchanging heat between a transfer fluid and the combustion chamber (4) to transfer a portion of the thermal energy of the combustion to a user device (13). The system further comprises a loop (20) for recirculating a first fraction (22) of the exhaust gases coming from the combustion chamber (4), the loop having a gas extraction inlet downstream of the combustion chamber (4) and a gas injection outlet upstream of the burner means (3).

Description

[Technical Field]

[0001] The present invention relates to a system for producing thermal energy from the combustion of metals, particularly for use in domestic heating or industrial buildings or facilities in remote areas, as well as in industrial heat generation applications. The invention also encompasses a method for producing thermal energy implemented in this system. [Background technology]

[0002] Most current heating systems (natural gas, propane, butane, or fuel oil boilers) use fuels that emit CO2. Furthermore, in many countries around the world, rising energy costs and the risk of supply shortages associated with energy dependency are driving the search for alternative green energy sources for domestic and commercial heating, as well as for industrial heat-requiring appliances. The use of wood for heating also presents significant deforestation risks if responsible and sustainable forest management practices are not adopted.

[0003] In this context, as detailed in the paper "Direct Combustion of Recyclable Metal Fuels for Zero-Carbon Heat and Power" by J.F. Bergthorson, Applied Energy, 2015, the combustion of metal particles is one solution that has been proposed to generate CO2-emission-free combustion for all types of power generation applications. Metal fuels (magnesium, aluminum, iron) have the advantage of producing only solid metal oxides during combustion, which can be easily recovered in combustion systems. These can then be reused using renewable energy by inert anode electrolysis or solar-assisted zero-CO2 thermochemical reduction.

[0004] Combustion of metal particles has long been used in aerospace propulsion applications, as well as for internal and external combustion automotive applications (see U.S. Patent No. 8,100,095 (B2)). In International Publication No. 2023,028,697 (A1), the proposed solution does not reduce nanometer iron oxide emissions because the oxygen concentration is not adjustable, which is crucial for minimizing these emissions and optimizing the overall energy or material yield of the metal cycle (Stereoscopic High-Speed ​​Imaging of Iron Microexplosions and Nanoparticle-Release, Li et al., Vol. 29, Optics Express, 2021). Indeed, the mass of the nanoparticles generated means that energy must subsequently be consumed to regenerate the microparticles and regenerate the initial fuel.

[0005] Furthermore, the exhaust mass loss associated with these nanoparticle emissions affects the number of cycles possible with the same amount of material: Recovering 99% of the oxide mass instead of 99.9% reduces the number of times the same mass of iron can be burned and reused by a factor of 10.

[0006] The main objective of the present invention is to propose a solution to reduce the emission of oxide nanoparticles. Another objective of the present invention is to facilitate flame ignition compared to the prior art described in the above-mentioned documents which disclose flame ignition by gas / particle premixtures in air. Summary of the Invention

[0007] Disclosure of the Invention The object is to provide a system for producing thermal energy from the combustion of metal particles, comprising: - means for burning metal particles in a combustion chamber, comprising an ignition system intended to generate a pilot flame; means for injecting metal particles into said burner means; - means for introducing air to be injected into the burner means to form a premix of air and metal particles, said means comprising fan means; - means for capturing oxidized particles in the exhaust gases, downstream of or associated with the first heat exchange means; - first heat exchange means between a transfer fluid and the combustion chamber, said transfer fluid being injected into said heat exchange means via pump means and intended to transfer a portion of the combustion heat energy to a user device; The system is characterized in that it further comprises a loop for recirculating a first fraction of the exhaust gas coming from the combustion chamber, which loop is achieved by a system having a gas extraction inlet downstream of the combustion chamber and a gas injection outlet upstream of the burner means.

[0008] In a first embodiment, the re-injection outlet of the recirculation loop is located downstream of the air intake means, more particularly between the metal particle injection means and the burner means.

[0009] In a second embodiment, the re-injection outlet of the recirculation loop is located upstream of the air intake means.

[0010] The air intake means may further advantageously comprise additional means for adjusting the air intake flow rate.

[0011] The generation system according to the invention may further comprise fan means for extracting exhaust gases downstream of the capture means.

[0012] The recirculation loop may advantageously be provided with means for regulating the recirculation flow rate and with fan means.

[0013] In a particular version of the invention, the production system according to the invention may further comprise means for preheating the intake air upstream of its injection into the burner means, these preheating means comprising second means for heat exchange between a second fraction of the exhaust gases from the combustion chamber and the intake air.

[0014] The first heat exchange means may advantageously comprise an enclosure arranged to surround the combustion chamber and to circulate the transfer fluid therein. This heat exchange enclosure may also surround the filtering means.

[0015] In a first group of applications of the generating system according to the invention, the transfer fluid is water which is injected into the first heat exchange means via a water pump. This system can be used in central heating or domestic hot water heating installations.

[0016] In a second group of applications of the production system according to the invention, the transfer fluid is air, which is injected into the second heat exchange means via fan means. This system can be implemented in a room air heating installation or a wet product drying installation, which comprises (i) a drying drum, at its inlet, intended to receive, on the one hand, hot air from the second heat exchange means and, on the other hand, wet product from the wet product storage unit, and (ii) at its outlet, to deliver the dried product and cooled dry air to a recovery unit.

[0017] In a third group of applications of the generating system according to the invention, the transfer fluid is steam injected into the second heat exchange means via a steam pump, and the generating system further comprises an air recirculation loop intended to receive at its inlet cooled steam from a user device and inject it into the inlet of said steam pump. The generating system according to the invention further comprises excess steam in the steam recirculation loop and can be implemented in installations for drying wet products or in industrial systems consuming the heat transported by steam.

[0018] In a fourth group of applications of the present invention, the fluid is two-phase, (i) in liquid form upstream of the first heat exchange means and (ii) in vapor form downstream of the first heat exchange means and at the inlet to the user device, and the production system according to the present invention further comprises means for condensing the cooled vapor from the user device and injecting it in liquid form into the pump means.

[0019] The condensing means cooperates with means for recovering thermal energy during condensation for the purpose of recovering waste heat from the energy conversion.The user device may comprise a high pressure steam turbine driving an electrical generator.

[0020] According to another aspect of the invention, there is provided a method for producing thermal energy from the combustion of metal particles, implemented in a production system according to the invention, the method comprising: - mixing air from the air intake with metal particles from the metal particle injection; - injecting a mixture of air and metal particles into the burner; - burning the mixture in a combustion chamber to produce heat and exhaust gases; - exchanging the heat thus generated within the user device via a transfer fluid; capturing oxidized particles from the exhaust gas downstream of the burner, A method is proposed, wherein the method further comprises recirculating a first exhaust gas fraction, the recirculation comprising withdrawal downstream of the combustion chamber and injection of the first exhaust gas fraction upstream of the burner means.

[0021] The exhaust gas injection can be downstream of the metal particle injection or upstream of the air intake. [Brief explanation of the drawings]

[0022] Further features and advantages will become apparent from the following description of particular, non-limiting embodiments of the invention, which proceeds with reference to the drawings. [Figure 1] 1 is a schematic diagram of a domestic hot water system (for domestic use and / or space heating). [Figure 2] 1 is a schematic diagram of a domestic hot water system (for domestic and / or space heating) with a large exhaust gas recirculation loop. [Figure 3] 1 is a schematic diagram of a residential air heating system. [Figure 4]1 is a schematic diagram of a system for indirect hot air drying of wet products in the chemical, construction, and other industries. [Figure 5] 1 is a schematic diagram of an indirect closed-loop heated steam drying system for wet products in the chemical, construction, and other industries. [Figure 6] 1 is a schematic diagram of a steam generation system for an industry (such as a brewery). [Figure 7] 1 is a schematic diagram of a Rankine cycle power generation system (organic liquid, also known as steam or ORC). [Figure 8] FIG. 1 is a schematic diagram of a combined heat and power system that uses a Rankine cycle and a heat recovery unit in the condenser to recover waste heat and maximize overall efficiency. DETAILED DESCRIPTION OF THE INVENTION

[0023] Some examples of energy generation systems according to the present invention will now be described with reference to the above figures, it being noted that components and modules common to the various examples shown have common reference numbers.

[0024] 1, a boiler / heater type thermal energy generation system S1 comprises an injector 100 for metal particles, a burner 3 for metal particles burned in a fixed volume combustion chamber 4 connected to a duct 20 for drawing in a fraction 22 of the exhaust gases that is a component of a recirculation loop 20, the reinjection outlet of which is located downstream of the particle injector 100 and upstream of the inlet of the burner 3. Another fraction 23 of the exhaust gases passes through a heat exchanger 100 to heat the intake air and is extracted by the action of an extraction fan 11.

[0025] The exhaust gases, which consist of metal oxides and nitrogen (magnesium, iron, or aluminum oxide depending on which of the three fuels is used), pass through a filtration system 8 and then through a heat recovery unit 1.

[0026] It should be noted that the filtration system and heat recovery unit 1 can be nested or cascaded.

[0027] The metal particle injector 100 can take the form of a fluidized aerosol generator that injects particles into an air stream with the aid of a Venturi system. Alternatively, the particles can be injected by gravity through a vibrating (or non-vibrating) funnel on the air line, with a gentle fluidizing flow applied at the funnel inlet to prevent clogging of the outlet. Another possibility is to use a worm screw, the diameter and rotation speed of which allow the precision and flow rate of the powder injection to be controlled within the air duct receiving the powder.

[0028] The metal burner 4 can be constructed using a swirler to increase the air injection velocity without having to worry about the pilot flame generated by the ignition system 2 erupting. The principle is to inject part of the airflow axially and another part tangentially using a tangential tube or stationary turbine to create a shear and recirculation zone toward the interior of the burner 3 (the vacuum effect within the vortex generated by the centrifugal flow) and promote flame stabilization. This aerodynamic stabilization mechanism creates a zone in the flow where the velocity is low enough to approach that of the metal flame, thus ensuring that the flame is anchored to the burner. This mechanism becomes increasingly important as air loads increase and the fuel involved has a relatively low flame speed. Swirl intensity control allows the flame size and its overall morphology to be managed.

[0029] To achieve continuous stabilization of the metal flame, when using only iron powder, the combustion air entering the system can be preheated. To compensate for the heat released per unit volume during iron combustion and reduce the use of natural gas in the pilot flame to facilitate its ignition, it may be useful to add an intake air preheating block 1 that recovers waste heat from the system's exhaust. Iron flames are more difficult to stabilize than magnesium or aluminum flames due to the low reaction rate associated with heterogeneous combustion and the oxide layer around the particles, which greatly reduces the heat release rate and therefore the reaction temperature.

[0030] This has a detrimental effect on flame stabilization, which is hindered by convective and radiative losses. The addition of heat from the exhaust gas increases overall energy efficiency and reduces the amount of gas in the pilot flame, thus reducing CO2 emissions.

[0031] The intake air preheating system consists of a gas-to-gas exchanger 1, which recovers waste heat energy from the main exhaust circuit and transfers it in a secondary circuit (serpentine tube, or any geometric shape that maximizes the exchange surface, such as a plate heat exchanger) to the intake air drawn in by the fan and directed to the burner for combustion air supply.

[0032] The pilot flame can take the form of a methane (or propane or butane) injector 2, positioned in the direction of the axial flow of iron and air, generating a diffusion flame, or a methane / iron / air hybrid flame premixed by adding methane to the axial duct carrying the particles into the air. A spark, activated by a remote actuator, can ignite the pilot flame and thus stabilize the iron flame. In the case of aluminum or magnesium, this pilot flame can be extinguished as soon as stabilization is achieved, due to their high-temperature homogeneous combustion, which facilitates the self-sustaining of the flame.

[0033] The combustion system is also optimized by the addition of exhaust gas recirculation 20, composed mostly of nitrogen, through a secondary circuit to adjust the oxygen percentage of the mixture around the iron particles.

[0034] This secondary recirculation circuit 20 comprises an exhaust gas extraction fan 9 and a controlled butterfly valve 10 for adjusting the recirculation flow rate.

[0035] High oxygen concentrations, similar to those in ambient air, locally increase the reaction rate and therefore the particle temperature, raising the particle temperature locally above the boiling point of iron (3134 K), increasing the risk of particle microexplosions (depending on the temperature and expansion rate of the gas formed within the particle), and ultimately potentially producing oxide nanoparticles with a micron size distribution that are very difficult to filter and regenerate into pure iron [Stereoscopic high-speed imaging of iron microexplosions and nanoparticle-release, Li et al., Vol. 29, Optics Express, 2021].

[0036] This is a problem when iron is used as a recirculating fuel. Using exhaust gas recirculation to reduce the oxygen concentration to 14% significantly reduces the appearance of oxide nanoparticle clouds by lowering the reaction temperature and, therefore, the particle temperature. The latter leads to a rapid decrease in the metal's saturated vapor pressure, thus significantly reducing its evaporation [Critical temperature for nanoparticle cloud formation during combustion of single micron-sized iron particle, Ning et al., Combustion and Flame 244, 2022].

[0037] Because oxygen concentration plays a dominant role in the overall concentration of a fuel-lean mixture, the closer the concentration is to stoichiometry, the more important it becomes for oxygen transport and, therefore, reaction temperature. A substoichiometric overall concentration is necessary to avoid the deposition of unburned metal particles. Radiative heat loss increases as the temperature of these particles rises rapidly, again preventing stabilization and leading to a rapid increase in NOx emissions.

[0038] A more general effect of exhaust gas recirculation applied to combustion is the reduction of thermal nitrogen oxide emissions by lowering the combustion temperature (Zel'dovich mechanism).

[0039] The exhaust gas recirculation system preferably consists of a duct connected to the exhaust duct downstream of the filtration system, which removes gas consisting essentially of nitrogen (and excess oxygen in the case of near-stoichiometric combustion) by means of an suction fan followed by a recirculation flow-regulating butterfly valve in order to reinject this gas upstream of the burner or directly into the intake duct upstream of the main fan (in which case the suction fan is no longer necessary).

[0040] The recirculation rate can vary from 0 to over 50% of the total injection flow (NOx emission reductions plateau above 50%), and an oxygen concentration of approximately 14% already significantly reduces the formation of oxide nanoparticles (although this system allows for oxygen concentrations in the intake air to be reduced to as low as 10%). Therefore, in cyclical energy applications where the goal is to regenerate initial iron particles from oxides, minimizing the impact of generating nanoparticle emissions allows particle integrity to be maintained throughout the cycle, avoiding intermediate reforming methods for micrometer iron particles.

[0041] The oxide capture means 8 may comprise a set of cyclones sized to filter oxide particles in the range of a few microns to a few hundred microns in size, a common method in industrial dust removal. Alternatively, a settling chamber may be implemented that utilizes the inertia of larger particles with diameters in the range of a few microns to a few hundred microns, which settle to the bottom of the chamber under the influence of gravity.

[0042] The remaining nanoparticles can be filtered using a bag filter or a HEPA (high efficiency particulate air) filter, or an electrostatic or electromagnetic filter with downstream suction ventilation to overcome the pressure drop created by the filtering element.

[0043] The energy generation system S2 according to the invention can be used to heat domestic air, domestic water (domestic and heating) (S1), to generate steam for industry (S5), to dry aggregates or any wet product (S3, S4), to generate electricity in a steam or organic liquid Rankine cycle (S6), or for combined heat and power if heat is recovered in the condenser (S7).

[0044] The system S1 for generating thermal energy from the combustion of metal particles comprises an ignition system 2 intended to generate a pilot flame, means 3 for burning metal particles in a combustion chamber 4, means 100 for injecting metal particles into said burner means, means 5, 6 for taking in air that is injected into the burner means 3 so as to form a premixture of air and metal particles, comprising fan means 5 (of the blower fan type) and means 6 for adjusting the air intake flow rate, means for capturing oxidized particles in the exhaust gases, downstream of the first heat exchange means, means 11 for extracting the exhaust gases downstream of the capture means, a heat exchanger 7 between a transfer fluid and the combustion chamber 4, this transfer fluid being injected into the heat exchange means 7 via pump means 12 and intended to transfer part of the combustion thermal energy to a user device 13.

[0045] The heat exchanger 7 may consist of a set of tubes through which a heat transfer fluid circulates, transporting heat to the user device. These tubes may be located within the high-temperature volumes of the combustion chamber and filtration system, or may be arranged around them but in contact with their walls. The heat transfer fluid may be distributed among several parallel-arranged tubes or in a coil to maximize the heat exchange surface with the high-temperature flow from the combustion chamber.

[0046] The production system S1 further comprises a loop for recirculating a fraction of the exhaust gas coming from the combustion chamber 4, the loop having a gas extraction inlet downstream of the combustion chamber 4 and a gas injection outlet upstream of the burner means 3.

[0047] Referring to Figure 2, the production system S2 is a variant of the system S1 and comprises a large recirculation loop 30 for a fraction of the exhaust gases from the combustion chamber 4, with a gas extraction inlet downstream of the combustion chamber 4 and a gas injection outlet 32 ​​upstream of the inlet of the fan means 5 for air intake, and optionally a control unit 10.

[0048] 3, the production system S3 is a variant of the system S1 for heating air by combustion of metal particles: instead of the heat exchanger 13, it comprises a gas-air heat exchanger 13b.

[0049] With reference to FIG. 4 , the production system S4 is a variant of embodiments S1-3, implemented in an installation for drying a wet product, this installation 13c comprising (i) an inlet, a drying drum 14 intended to receive, on the one hand, hot air from the second heat exchange means 7 and, on the other hand, a wet product from the wet product storage unit 13c, and (ii) an outlet, to deliver the dried product to the recovery unit 15 and to deliver cooled dry air.

[0050] Referring to FIG. 5, the generation system S5 is a variation of the generation system S4, in which the transfer fluid is steam injected into the heat exchanger 7 by the steam pump 12, and the system further comprises an air recirculation loop 50 designed to receive cooled steam from the user device 13c at its inlet and inject it into the inlet of the steam pump 12.

[0051] Referring to FIG. 6, generation system S6 is a variation of generation system embodiments S1-S4 that transfers combustion heat to a steam transport heat consuming industrial system 13d comprised of steam generator elements.

[0052] Referring to Figure 7, generation system S7 is a variation of embodiment S6, in which the transfer fluid is two-phase: (i) in liquid form upstream of heat exchanger 7, and (ii) in vapor form downstream of heat exchanger 7 and at the inlet to user device 17. This generation system 7 further comprises a loop 70 for recovering the cooled vapor leaving user device 17, directing it to the inlet of condensing unit 18, and injecting it in liquid form into pumping means 15. User device 17 includes a high-pressure steam turbine driving generator 13. System S7 can use a Rankine cycle, but also a Stirling-type thermodynamic converter or a gas turbine-type converter with external combustion, in which the combustion gases are heated by an exchanger and the expanded gases pass through a turbine; however, in multi-MW applications, Rankine cycle converters (organic liquid or vapor) are often used due to their economic efficiency.

[0053] Referring to FIG. 8, the generation system S8 is a variant of embodiment S7, in which the condensation means 14 are inserted in a recovery loop 70 and cooperate with a device 19 designed to recover thermal energy during condensation with the aim of recovering waste heat from the energy conversion.

[0054] Naturally, the invention is not limited to the examples described above, and many other embodiments can be envisaged without departing from the scope of the invention. In particular, the on-board energy generation system can be used to propel mobile systems and devices, such as ships, railway systems, spacecraft, aircraft, and in particular airships.

[0055] The thermal energy generation system according to the invention can also be implemented on the Moon by utilizing metal particles and oxygen from the reduction process of the regolith that covers the soil.

Claims

1. 1. A system (S1-S8) for generating thermal energy from the combustion of metal particles, comprising: - means (3) for burning metal particles in a combustion chamber (4), comprising an ignition system (2) intended to generate a pilot flame; - means (100) for injecting metal particles into said burner means; - means (5, 6) for taking in air to be injected into said burner means (3) so as to form a premixture of air and metal particles, comprising fan means (5); - means (8) for capturing oxidized particles in the exhaust gases, downstream of or associated with the first heat exchange means; - first heat exchange means (7) between a transfer fluid and said combustion chamber (4), said transfer fluid being injected into said heat exchange means (7) via pump means (12) and intended to transfer a part of the combustion thermal energy to a user device (13, 13b, 13c, 13d, 17), characterized in that said system further comprises a loop (20) for recirculating a first fraction (22) of the exhaust gases coming from said combustion chamber (4), having a gas extraction inlet downstream of said combustion chamber (4) and a gas injection outlet upstream of said burner means (3).

2. 2. A production system (S1) according to claim 1, characterized in that the reinjection outlet of the recirculation loop is arranged downstream of the air intake means.

3. 3. A generating system (S1) according to claim 2, characterized in that said recirculation loop (20) further comprises fan means (9).

4. 2. A production system (S2) according to claim 1, characterized in that the reinjection outlet of the recirculation loop is arranged upstream of the air intake means (5, 6).

5. A generation system according to any one of claims 1 to 4, characterized in that the air intake means further comprise additional means (6) for adjusting the air intake flow rate.

6. A generating system according to any one of claims 1 to 5, characterized in that it further comprises fan means (11) for extracting exhaust gases downstream of the capture means.

7. A production system according to any one of claims 1 to 6, characterized in that the recirculation loop (20, 30) comprises means (10) for adjusting the recirculation flow rate.

8. 8. The generation system (S1-S8) according to any one of claims 1 to 7, characterized in that the generation system (S1-S8) further comprises means for preheating intake air upstream of its injection into the burner means, the preheating means comprising second means (21) for heat exchange between a second fraction (23) of exhaust gases from the combustion chamber and the intake air (1).

9. A generation system (S1-S8) according to any one of claims 1 to 8, characterized in that the first heat exchange means (7) comprises an enclosure arranged to surround the combustion chamber (4) and to circulate the transfer fluid inside.

10. A generating system (S1-S8) according to claim 9, characterized in that the heat exchange enclosure (7) also encloses an oxide trapping means (8).

11. A production system (S1) according to any one of claims 1 to 10, characterized in that the transfer fluid is water which is injected into the first heat exchange means (7) via a water pump (12).

12. The generating system (S1) according to claim 11, implemented in a central heating installation for a room (13).

13. 13. A generating system (S1) according to claim 11 or 12, implemented in a hot water heating installation (13).

14. A generation system (S3) according to any one of claims 1 to 10, characterized in that said transfer fluid is air injected into the second heat exchange means (7) via fan means (12).

15. The generating system (S3) according to claim 14, implemented in an indoor air heating installation (13b).

16. 15. The production system (S4) according to claim 14, implemented in an installation for drying a wet product, said installation (13c) comprising (i) a drying drum (14) intended at an inlet to receive, on the one hand, hot air from the second heat exchange means (7) and, on the other hand, wet product from the wet product storage unit (13c), and (ii) at an outlet to deliver the dried product to a recovery unit (15) and to deliver cooled dry air.

17. A generation system (S5) according to any one of claims 1 to 10, characterized in that the transmission fluid is steam injected into the second heat exchange means (7) via a steam pump (12), and the generation system (S5) further comprises a recirculation loop intended to receive cooled steam from a user device (13c) at the inlet and inject it into the inlet of the steam pump (12).

18. 18. The generating system (S5) of claim 17, further comprising means for venting excess steam in the steam recirculation loop.

19. 19. A production system (S5) according to claim 17 or 18, implemented in an installation for drying wet products.

20. 19. A generation system (S6) according to claim 17 or 18, implemented in an industrial system (13d) that consumes heat transported by steam.

21. 11. The generation system (S7, S8) according to any one of claims 1 to 10, characterized in that the fluid is two-phase, (i) in liquid form upstream of the first heat exchange means (7) and (ii) in vapor form downstream of the first heat exchange means (7) and at the inlet to the user device (17), and the generation system (S7, S8) further comprises means (18, 19) for condensing cooled vapor from the user device (17) and injecting it in liquid form into the pump means (15).

22. 22. A generation system (S8) according to claim 21, characterized in that the condensation means (19) cooperate with means for recovering thermal energy during condensation, with the aim of recovering waste heat from the energy conversion.

23. 23. A generation system (S7, S8) according to claim 21 or 22, characterized in that the user device comprises a high-pressure steam turbine (17) driving a generator (13e).

24. A method for producing thermal energy from the combustion of metal particles, implemented in a production system (S1-S7) according to any one of claims 1 to 23, comprising: - mixing air from the air intake with metal particles from the metal particle injection; - injecting a mixture of air and metal particles into the burner (3); - burning this mixture in a combustion chamber (4) to produce heat and exhaust gases; - exchanging the heat thus produced within the user device (13, 13b, 13c, 13d, 12) via a transfer fluid; - capturing particles from the exhaust gases downstream of said burner (3), The method further comprises recirculating a first exhaust gas fraction (22), wherein said recirculation comprises withdrawal downstream of said combustion chamber (4) and injection of said first exhaust gas fraction upstream of said burner means (3).

25. 25. The method (S1) according to claim 24, characterized in that the exhaust gas injection is carried out downstream of the air intake.

26. 25. The method (S2) according to claim 24, characterized in that the exhaust gas injection is carried out upstream of the air intake.

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