System and method for producing thermal energy using metal powder as fuel

Abstract

The invention relates to a system (S1) for producing thermal energy from the combustion of metal particles, comprising: a metal particle burner located in a combustion chamber (4); a device (100) for injecting metal particles into the burner device; means (5, 6) for suctioning air in order to form a pre-mixture of air and metal particles; means for capturing oxidizing particles in the exhaust gas, either downstream of or in combination with the first heat exchange means; and a heat exchanger (7) for exchanging heat between a transfer fluid and the combustion chamber (4), the heat exchanger for transferring a portion of the combustion thermal energy to a user device (13). The system further comprises a circuit (20) for recirculating a first portion (22) of the exhaust gas from the combustion chamber (4), the circuit having a gas extraction inlet downstream of the combustion chamber (4) and a gas injection outlet upstream of the burner device (3).

Description

Technical Field

[0001] The present invention relates to a system for producing thermal energy from the combustion of metals, in particular for domestic heating or for industrial buildings or installations in remote areas, as well as for industrial heat production applications. The invention also covers a method for producing thermal energy implemented in the system. Existing technology

[0002] Most current heating systems (natural gas, propane, butane, or oil-fired boilers) use fuels that emit CO2. Furthermore, rising energy costs and the risk of shortages associated with energy dependence in many countries around the world are driving the search for alternative green energy sources for residential and commercial heating, as well as for equipment requiring industrial heat. Using wood for heating also carries significant deforestation risks if reliable, sustainable forest management is not adopted.

[0003] In this context, the combustion of metal pellets (as detailed in JF Bergthorson's 2015 article, "Direct combustion of recyclable metal fuels for zero-carbon heat and power," published in Applied Energy) is a solution for producing CO₂-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 the combustion system. These metal fuels can then be recycled using renewable energy through inert anode electrolysis or solar-assisted zero-CO₂ thermochemical reduction.

[0004] The combustion of metal particles has long been used in aerospace propulsion applications and has also been used for internal and external combustion automotive applications in document US8100095B2. In WO2023028697A1, the solution proposed does not reduce the emissions of nanoscale iron oxides because the oxygen concentration cannot be adjusted, which is crucial to minimize these emissions and optimize 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]. In fact, the mass of the nanoparticles produced means that energy must be consumed to subsequently reform the microparticles in order to reproduce the initial fuel.

[0005] Furthermore, the exhaust mass penalty associated with these nanoparticle emissions affects the number of cycles possible using 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 recycled by a factor of ten.

[0006] The main object of the present invention is to provide a solution for reducing oxide nanoparticle emissions.Another object of the present invention is to facilitate flame ignition compared to the prior art described in the above document, which discloses flame ignition by a gas / particle premixture in air. Summary of the Invention

[0007] This object is achieved by a system for producing thermal energy from the combustion of metal particles, comprising:

[0008] - a device for burning metal particles in a combustion chamber, comprising an ignition system for generating a pilot flame,

[0009] - means for injecting metal particles into the burner device,

[0010] - means for drawing in air for injection into the burner means in order to form a premix of air and metal particles, the means comprising fan means,

[0011] - a device for capturing oxidized particles in the exhaust gas, said device being located downstream of the first heat exchange device or being integrated with said first heat exchange device,

[0012] - a first heat exchange device located between a transfer fluid and the combustion chamber, the transfer fluid being intended to be injected into the heat exchange device via pumping means and to transfer a portion of the combustion heat energy to a user device,

[0013] Characterized in that the system further comprises a circuit for recirculating a first portion of the exhaust gases coming from the combustion chamber, the circuit having a gas extraction inlet situated downstream of the combustion chamber and a gas injection outlet situated upstream of the burner device.

[0014] In a first embodiment, the re-injection outlet of the recirculation loop is arranged downstream of the air intake device and more specifically between the metal particles injection device and the burner device.

[0015] In a second embodiment, the re-injection outlet of the recirculation circuit is arranged upstream of the air intake device.

[0016] The air intake device may also advantageously comprise additional means for adjusting the intake air flow rate.

[0017] The production system according to the invention may also comprise fan means for extracting the exhaust gases downstream of the capture means.

[0018] The recirculation circuit may advantageously comprise means for regulating the recirculation flow rate as well as fan means.

[0019] In a particular version of the invention, the production system according to the invention may also comprise means for preheating the intake air upstream of the intake air injection burner means, these preheating means comprising second means for exchanging heat between a second portion of the exhaust gases from the combustion chamber and the intake air.

[0020] The first heat exchange means may advantageously comprise a housing surrounding the combustion chamber and arranged to circulate the transfer fluid therein. The heat exchange housing may also surround the filtering means.

[0021] In a first family of applications of the production system according to the invention, the transfer fluid is water injected into the first heat exchange device via a water pump. The system can be used in central space heating or domestic hot water heating installations.

[0022] In a second family of applications of the production system according to the invention, the transfer fluid is air injected into the second heat exchange device via a fan device. The system can be implemented in a room air heating facility or a wet product drying facility comprising a drying drum intended to (i) receive at its inlet the hot air from the second heat exchange device and the wet product from the wet product storage unit, and (ii) deliver at its outlet the dried product to a recovery unit and to deliver cooled dry air.

[0023] In a third family of applications of the production system according to the present invention, the transfer fluid is steam injected into the second heat exchange device via a steam pump, and the production system further comprises an air recirculation loop, which is designed to receive cooled steam from the user equipment at its inlet and inject this cooled steam into the inlet of the steam pump. The production system according to the present invention may also include excess steam in the steam recirculation loop and may be implemented in facilities for drying wet products or in industrial systems for consuming heat transported by steam.

[0024] In a fourth family of applications of the present invention, the fluid is two-phase (i) in liquid form upstream of the first heat exchange device, and (ii) in vapor form downstream of the first heat exchange device and at the inlet to the user equipment, and the production system according to the present invention also includes a device for condensing the cooling vapor from the user equipment and injecting the cooling vapor into the pump device in liquid form.

[0025] The condensing device is coupled with a device for recovering thermal energy during condensation to recover waste heat from the energy conversion.The user equipment may include a high pressure steam turbine that drives an electrical generator.

[0026] According to another aspect of the present invention, a method for producing thermal energy from the combustion of metal particles is proposed, which method is implemented in a production system according to the present invention and comprises the following steps:

[0027] - mixing the air from the air intake and the metal particles from the metal particle injection,

[0028] - A mixture of air and metal particles is injected into the burner,

[0029] - burning the mixture in a combustion chamber, thereby producing heat and exhaust gases,

[0030] - exchanging the heat thus produced via a transfer fluid in the user device,

[0031] - capture of oxidized particles from the exhaust gases downstream of the burner,

[0032] Characterized in that the method further comprises recirculating the first exhaust gas portion, the recirculation comprising extraction downstream of the combustion chamber and injection of the first exhaust gas portion upstream of the burner device.

[0033] This exhaust gas injection can be performed downstream of the metal particle injection or upstream of the air intake. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Further features and advantages will become apparent from the following description of specific non-limiting embodiments of the invention with reference to the accompanying drawings, in which:

[0035] [ Figure 1 ] is a diagram of a domestic plumbing system (sanitary and / or heating).

[0036] [ Figure 2 ] is a schematic diagram of a domestic water heating system (sanitary and / or heating) with a large exhaust gas recirculation loop.

[0037] [ Figure 3 ] is a schematic diagram of a residential air heating system.

[0038] [ Figure 4 ] is a schematic diagram of a system used for indirect hot air drying of moist products in the chemical, construction, and other industries.

[0039] [ Figure 5 ] is a schematic diagram of an indirect closed-loop heated steam drying system for moist products in the chemical, construction, and other industries.

[0040] [ Figure 6 ] is a schematic diagram of a steam generation system for industrial (breweries, etc.)

[0041] [ Figure 7] is a schematic diagram of a Rankine cycle power generation system (steam or organic liquid, called ORC).

[0042] [ Figure 8 ] 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

[0043] With reference to the above-mentioned figures, several examples of energy production systems according to the present invention will now be described. Note that components and modules common to the various examples shown have common reference numerals.

[0044] refer to[ Figure 1 ], a boiler / heater type thermal energy production system S1 comprises: a metal pellet injector 100; a burner 3 for burning metal pellets in a fixed-volume combustion chamber 4; and the combustion chamber 4, which is connected to a pipe 20 for sucking in a portion 22 of the exhaust gas, the pipe being part of a recirculation loop 20, the re-injection outlet of which is arranged downstream of the pellet injector 100 and upstream of the inlet of the burner 3. Another portion 23 of the exhaust gas passes through a heat exchanger 1 to heat the intake air and is extracted by the action of an extraction fan 11.

[0045] The exhaust gases consist of metal oxides and nitrogen (magnesium oxides, iron oxides or aluminum oxides, depending on which of the three fuels is used) and pass through a filter system 8 and then through a heat recovery unit 1 .

[0046] It should be noted that the filtration system and the heat recovery unit 1 can be nested or cascaded.

[0047] The metal particle injector 100 can take the form of a fluidized aerosol generator that injects particles into the 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 added at the funnel inlet to prevent clogging of the outlet. Another possibility is the use of an worm screw, the diameter and rotational speed of which allow for controlled precision and flow rate of powder injection into the air line receiving the powder.

[0048] The metal burner 4 can be constructed using a swirler, which increases the air injection rate without having to worry about blowing out the pilot flame generated by the ignition system 2. The principle is to inject part of the airflow axially and the other part tangentially using a tangential tube or static turbine to create a shear and recirculation zone (the vacuum effect within the vortex generated by the centrifugal flow) toward the interior of the burner 3 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, ensuring flame attachment to the burner. This mechanism becomes more important when the air load increases and the fuel involved has a relatively low flame speed. Controlling the swirl intensity allows for the size of the flame and its overall shape to be managed.

[0049] To achieve continuous stabilization of the metal flame, the combustion air entering the system can be preheated when using only iron powder. To reduce the use of natural gas in the pilot flame (which replenishes the heat released per unit volume during iron combustion and facilitates its ignition), it may be useful to add an 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 surrounding the particles, which significantly reduces the heat release rate and, therefore, the reaction temperature.

[0050] This has a detrimental effect on flame stability, as convection and radiation losses can destroy flame stability.The addition of heat from the exhaust gases improves overall energy efficiency and reduces the amount of gas in the pilot flame and therefore reduces CO2 emissions.

[0051] The intake air preheating system consists of a gas-gas exchanger 1 that recovers waste heat energy from the primary exhaust circuit and transfers it in a secondary circuit (serpentine, or any geometry that maximizes the exchange surface, such as a plate heat exchanger) to the intake air, which is sucked in by a fan and directed to the burner to supply the combustion air.

[0052] The pilot flame can take the form of a methane (or propane or butane) injector 2 placed in the axial flow direction of the iron and air (this creates a diffusion flame), or a methane / iron / air mixture flame premixed by adding methane to the axial duct that carries the particles into the air. A spark activated by a remote actuator can ignite the pilot flame, thereby stabilizing the iron flame. In the case of aluminum or magnesium, due to their high temperatures and homogeneous combustion, the pilot flame can be extinguished once stability is achieved, which promotes flame self-sustaining.

[0053] The combustion system is also optimized by means of the addition of exhaust gas recirculation 20 consisting mainly of nitrogen through a secondary loop in order to adjust the oxygen percentage of the mixture surrounding the iron particles.

[0054] The secondary recirculation loop 20 comprises an exhaust gas extraction fan 9 and a controlled butterfly valve 10 for adjusting the recirculation flow rate.

[0055] High concentrations of oxygen, comparable to those in ambient air, may locally increase the reaction rate, thereby raising the temperature of the particle to locally above the boiling point of iron (3134 K), increasing the risk of particle microexplosions (depending on the temperature and expansion rate of the gases formed within the particle) and ultimately producing oxide nanoparticles that are difficult to filter and regenerate back into pure iron at micron-sized particles [Stereoscopic high-speed imaging of iron microexplosions and nanoparticle-release, Li et al., Vol. 29, Optics Express, 2021].

[0056] This is problematic when iron is used as a recycled fuel. Using exhaust gas recirculation to reduce oxygen concentration by up to 14% significantly reduces the appearance of oxide nanoparticle clouds by lowering the reaction temperature and, therefore, the particle temperature. The latter causes a sharp drop in the saturated vapor pressure of the metal, which greatly reduces its evaporation [Critical temperature for nanoparticle cloud formation during combustion of single micron-sized ironparticle, Ning et al., Combustion and Flame 244, 2022].

[0057] Since oxygen concentration dominates the overall richness in lean fuel mixtures, richness becomes more significant for oxygen transport and, therefore, reaction temperature, for richnesses close to stoichiometric. To avoid the deposition of unburned metal particles, an overall richness below stoichiometry is desirable. As the temperature of these particles rises sharply, heat loss through radiation is also greater, which can also hamper stability and lead to a sharp increase in NOx emissions.

[0058] The more common effect of exhaust gas recirculation applied to combustion is to reduce thermal NOx emissions by lowering combustion temperatures (Zeldovich mechanism).

[0059] The exhaust gas recirculation system consists of a duct connected to the exhaust gas duct, preferably located downstream of the filtering system, which removes the gas consisting essentially of nitrogen (and excess oxygen in the case of near-stoichiometric combustion) by means of an extraction fan followed by a recirculation flow regulation butterfly valve, in order to reinject this gas upstream of the burner or directly into the intake duct upstream of the main fan (in this case, thanks to the main fan, the extraction fan is no longer necessary).

[0060] The recirculation rate can be varied from 0% to over 50% of the total injected flow (NOx emission reduction reaches a plateau after a recirculation rate of 50%), and an oxygen concentration of approximately 14% already significantly reduces the formation of oxide nanoparticles (although the oxygen concentration in the intake air can be reduced to 10% using this system). Therefore, in cyclic energy applications, where the goal is to regenerate the initial iron particles from the oxide, the impact of the produced nanoparticle emissions is minimized, allowing the particle integrity to be maintained throughout the cycle to avoid intermediate reforming of micron-sized iron particles.

[0061] The oxide capture device 8 may include a set of cyclones sized to filter oxide particles ranging from a few microns to several hundred microns. This is a common method used in industrial flue gas dust removal. Alternatively, a settling chamber may be implemented to utilize the inertia of larger particles ranging from a few microns to several hundred microns in diameter, which settle to the bottom of the chamber under the action of gravity.

[0062] Remaining nanoparticles can be filtered using bag filters or HEPA (High Efficiency Particulate Air) filters, or using electrostatic or electromagnetic filters with downstream suction ventilation to overcome the pressure drop generated by the filter element.

[0063] The energy production system S2 according to the invention can be used to heat domestic air, domestic water (sanitary and heating water) (S1), generate industrial steam (S5), dry aggregate or any wet product (S3, S4), generate electricity in a steam or organic liquid Rankine cycle (S6), or, if heat is recovered in the condenser, jointly generate heat and electricity (S7).

[0064] The system S1 for producing thermal energy from the combustion of metal particles comprises: a device 3 for burning metal particles in a combustion chamber 4, comprising an ignition system 2 intended to generate an ignition flame; a device 100 for injecting metal particles into the burner device; a device 5, 6 for sucking in air for injection into the burner device 3 in order to form a premix of air and metal particles, comprising a fan device 5 (blower fan type) and a device 6 for adjusting the intake air flow rate; a device for capturing oxidized particles in the exhaust gases downstream of a first heat exchange device; a device 11 for extracting the exhaust gases downstream of the capturing device; a heat exchanger 7, which is located between a transfer fluid and the combustion chamber 4, the transfer fluid being intended to be injected into the heat exchange device 7 via a pump device 12 and to transfer a portion of the combustion heat energy to a user device 13.

[0065] The heat exchanger 7 may consist of a set of tubes through which a heat transfer fluid circulates, thereby transferring heat to the user equipment. These tubes may be located within the thermal volume of the combustion chamber and the filtration system, or arranged around them but in contact with their walls. The heat transfer fluid is distributed either across several tubes arranged in parallel or in a coil, the purpose of which is to maximize the heat exchange surface with the heat flow from the combustion chamber.

[0066] The production system S1 also comprises a circuit for recycling a portion of the exhaust gases coming from the combustion chamber 4 , the circuit having a gas extraction inlet downstream of the combustion chamber 4 and a gas injection outlet upstream of the burner device 3 .

[0067] refer to[ Figure 2 ], the production system S2 is a variant of the system S1 (which includes a large recirculation loop 30 for a portion of the exhaust gases from the combustion chamber 4, the large recirculation loop having a gas extraction inlet located downstream of the combustion chamber 4, a gas injection outlet 32 ​​located upstream of the inlet for intake air of the fan device 5), and is optionally provided with a control unit 10.

[0068] refer to[ Figure 3 ], the production system S3 is a variant of the system S1 for heating air by combustion of metal particles. Instead of the exchanger 13, this production system comprises a gas-air exchanger 13b.

[0069] refer to[ Figure 4 ], the production system S4 is a variant of the embodiments S1-3, which is implemented in a facility for drying moist products, the facility 13c comprising a drying drum 14 intended to (i) receive, at an inlet, on the one hand, hot air from the second heat exchange device 7 and, on the other hand, moist products from a moist product storage unit 13c, and (ii) deliver, at an outlet, the dried products to a recovery unit 15 and to deliver cooled dry air.

[0070] refer to[ Figure 5 ], production system S5 is a variation of production system S4, in which the transfer fluid is steam injected into the heat exchanger 7 with the aid of a steam pump 12, and the system also includes an air recirculation loop 50, which is designed to receive cooled steam from the user device 13c at the inlet and inject the cooled steam at the inlet of the steam pump 12.

[0071] refer to[ Figure 6 ], production system S6 is a variant of production system implementation plans S1-S4, which transfers the combustion heat to an industrial system 13d consisting of elements of a steam generator that consumes the heat transported by the steam.

[0072] refer to[ Figure 7 ], production system S7 is a variant 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 production system 7 also includes 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 device 15. User device 17 includes a high-pressure steam turbine that drives generator 13. System S7 can use a Rankine cycle, or a Stirling-type thermodynamic converter or a gas turbine-type converter with external combustion, the combustion gases being heated by the exchanger and the expanded gases passing through the turbine, but for multi-MW applications, Rankine cycle converters (organic liquid or vapor) are more often used due to their economic efficiency.

[0073] refer to[ Figure 8 ], production system S8 is a variant of embodiment S7, in which the condensing device 14 is combined with a device 19 inserted in the recovery loop 70 and designed to recover thermal energy during condensation to recover waste heat from energy conversion.

[0074] Of course, the invention is not limited to the examples that have just been described, and many other embodiments are conceivable without departing from the scope of the invention. In particular, the onboard energy production system can be used to propel mobility systems and devices, such as ships, rail systems, spacecraft, aircraft, and in particular airships.

[0075] The thermal energy production system according to the invention can also be implemented on the Moon by using metal particles and oxygen obtained by a reduction process of the regolith covering the lunar soil.

Claims

1. A system (S1-S8) for producing thermal energy from the combustion of metal particles, the system comprising: - a device (3) for burning metal particles in a combustion chamber (4), comprising an ignition system (2) intended to generate an ignition flame, - means (100) for injecting metal particles into said burner means, - means (5, 6) for sucking in air for injection into said burner means (3) in order to form a premix of air and metal particles, comprising fan means (5), - a device (8) for capturing oxidized particles in the exhaust gas, located downstream of the first heat exchange device or combined with said first heat exchange device, - a first heat exchange device (7) situated between a transfer fluid and the combustion chamber (4), the transfer fluid being intended to be injected into the heat exchange device (7) via a pump device (12) and to transfer a portion of the combustion heat energy to a user device (13, 13b, 13c, 13d, 17), characterised in that the system further comprises a circuit (20) for recycling a first portion (22) of the exhaust gases from the combustion chamber (4), the circuit having a gas extraction inlet situated downstream of the combustion chamber (4) and a gas injection outlet situated upstream of the burner device (3).

2. Production system (S1) according to the preceding claim, characterized in that The re-injection outlet of the recirculation circuit is arranged downstream of the air intake device.

3. Production system (S1) according to the preceding claim, characterized in that The recirculation loop (20) further comprises a fan device (9).

4. The production system (S2) according to claim 1, characterized in that The re-injection outlet of the recirculation circuit is arranged upstream of the air intake device (5, 6).

5. Production system according to any one of the preceding claims, characterized in that The air intake device further comprises an additional device (6) for adjusting the intake air flow rate.

6. Production system according to any one of the preceding claims, characterized in that The production system further comprises fan means (11) for extracting exhaust gases downstream of the capture means.

7. Production system according to any one of the preceding claims, characterized in that The recirculation loop (20, 30) comprises a device (10) for adjusting the recirculation flow rate.

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

9. Production system (S1-S8) according to one of the preceding claims, characterized in that The first heat exchange device (7) comprises a housing surrounding the combustion chamber (4) and arranged to circulate the transfer fluid therein.

10. Production system (S1-S8) according to the preceding claim, characterized in that The heat exchange housing (7) also surrounds the oxide capture device (8).

11. Production system (S1) according to any one of the preceding claims, characterized in that The transfer fluid is water injected into the first heat exchange device (7) via a water pump (12).

12. Production system (S1) according to the preceding claim, which is implemented in a centrally heated installation in a room (13).

13. The production system (S1) according to the two preceding claims, which is implemented in a hot water heating installation (13).

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

15. Production system (S3) according to the preceding claim, which is implemented in a room air heating installation (13b).

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

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

18. Production system (S5) according to the preceding claim, characterized in that The production system also includes means for discharging excess steam in the steam recirculation loop.

19. Production system (S5) according to one of the two preceding claims, implemented in a facility for drying moist products.

20. Production system (S6) according to one of claims 17 or 18, which is implemented in an industrial system (13d) that consumes heat transported by steam.

21. The production 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 device (7), and (ii) in vapor form downstream of the first heat exchange device (7) and at the inlet to the user device (17), and the production system also includes means (18, 19) for condensing cooling vapor from the user device (17) and injecting the cooling vapor into the pump device (15) in liquid form.

22. Production system (S8) according to the preceding claim, characterized in that The condensing device (19) is combined with a device for recovering thermal energy during condensation, so as to recover waste heat from energy conversion.

23. Production system (S7, S8) according to one of the two preceding claims, characterized in that The user equipment includes a high-pressure steam turbine (17) that drives a generator (13e).

24. A method for producing thermal energy from the combustion of metal particles, said method being implemented in a production system (S1-S7) according to any one of the preceding claims, said method comprising the following steps: • Mixing air from the air intake with metal particles from the metal particle injection, • injecting said mixture of air and metal particles into the burner (3), • burning the mixture in a combustion chamber (4) to produce heat and exhaust gases, • exchanging the heat thus produced in said user equipment (13, 13b, 13c, 13d, 12) via a transfer fluid, • capture of particles from the exhaust gas downstream of the burner (3), Characterized in that the method further comprises recirculating a first exhaust gas portion (22), said recirculation comprising extraction downstream of the combustion chamber (4) and injection of said first exhaust gas portion upstream of the burner device (3).

25. The production method (S1) according to the preceding claim, characterized in that Exhaust gas injection is performed downstream of the air inlet.

26. The production method (S2) according to claim 24, characterized in that Exhaust gas injection is performed upstream of the air inlet.

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