WO2024175598A1

WO2024175598A1 - System and method for producing thermal energy using metal powder as a fuel

Info

Publication number: WO2024175598A1
Application number: PCT/EP2024/054295
Authority: WO
Inventors: Driss LARAQUI
Original assignee: Laraqui Driss
Priority date: 2023-02-20
Filing date: 2024-02-20
Publication date: 2024-08-29
Also published as: FR3145968A1; FR3145967B3; FR3145967A3

Abstract

The invention relates to a system (S1) for producing 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 intaking air so as to form a premix of air and metal particles, means for capturing the oxidised particles in the exhaust gases, either downstream or combined with first heat exchange means, and a heat exchanger (7) for exchanging heat between a transfer fluid and the combustion chamber (4), for transferring part of the thermal energy of the combustion to a user device (13). This 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

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

FIELD OF THE INVENTION

The present invention relates to a system for producing thermal energy by combustion of metals, in particular for application to domestic heating or industrial buildings or installations in remote areas, as well as for applications for producing industrial heat. It also relates to a method for producing thermal energy implemented in this system.

STATE OF THE ART

Most current heating systems (natural gas, propane, butane or fuel oil boilers) use fuels that emit CO2. In addition, the current increase in the cost of energy and the risk of shortages linked to the energy dependencies of many countries in the world are a reason for the search for a green alternative energy for residential and professional heating as well as for equipment requiring industrial heat. The use of wood for heating also presents a significant risk of deforestation if responsible and sustainable forest management is not adopted.

In this context, the combustion of metal particles, as detailed in the article “Direct combustion of recyclable metal fuels for zero-carbon heat and power”, Applied Energy, 2015 by J-F Bergthorson is a solution mentioned to produce combustion without CO2 emissions, for all types of energy production applications. Metallic fuels (magnesium, aluminum, iron) have the advantage of generating, during their combustion, only solid metal oxides that are easily recoverable in a combustion system. The latter can then be recycled using renewable energy through an inert anode electrolysis process or zero CO2 thermochemical reduction by solar energy.

The combustion of metal particles is historically known in aerospace propulsion applications or documents US8100095B2 for internal or external combustion automotive applications. In document WO2023028697A1, the proposed solution does not reduce nanometric iron oxide emissions because the oxygen concentration is not adjustable, but this concentration is critical to minimize these emissions and optimize the overall energy or material efficiency 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 nanoparticles produced implies having to spend energy to reform the micron particles a posteriori in order to reproduce the initial fuel.

In addition, the mass losses in the exhaust linked to these nanoparticle emissions influence the number of cycles possible with the same quantity of material. Recovering 99% of the mass of oxides instead of 99.9% reduces by a factor of 10 the number of times that the same mass of iron can be burned and recycled.

The main purpose of the invention is to propose a solution to reduce emissions of oxide nanoparticles. Another purpose of the invention is to facilitate the ignition of the flame compared to the state of the art set out in the aforementioned document which discloses ignition of the flame by means of a gas/particle premix in air.

des moyens pour brûler des particules métalliques dans une chambre de combustion, comprenant un système d’allumage prévu pour générer une flamme pilote,
des moyens pour injecter des particules métalliques dans lesdits moyens brûleurs,
des moyens d’admission de l’air à injecter dans les moyens brûleurs de façon à constituer un pré-mélange d’air et de particules métalliques, comprenant des moyens ventilateurs,
des moyens pour capturer les particules oxydées dans les gaz d’échappement, en aval ou combinés à des premiers moyens d’échange thermique,
des premiers moyens d’échange thermique entre un fluide de transfert et la chambre de combustion, ledit fluide de transfert étant prévu pour être injecté dans lesdits moyens d’échange thermique via des moyens de pompe et pour transférer une partie de l’énergie thermique de combustion dans un équipement utilisateur,

This objective is achieved with 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 adapted to generate a pilot flame,
means for injecting metal particles into said burner means,
means for admitting air to be injected into the burner means so as to constitute a premixture of air and metal particles, comprising fan means,
means for capturing oxidized particles in the exhaust gases, downstream or combined with first heat exchange means,
first means of heat exchange between a transfer fluid and the combustion chamber, said transfer fluid being provided to be injected into said heat exchange means via pump means and to transfer part of the thermal combustion energy into user equipment,

characterized in that it further comprises a recirculation loop for a first fraction of the exhaust gases from the combustion chamber, having a gas sampling inlet downstream of the combustion chamber and a gas injection outlet upstream of the burner means.

In a first embodiment, the reinjection outlet of the recirculation loop is arranged downstream of the air intake means, and more particularly between the metal particle injection means and the burner means.

In a second embodiment, the reinjection outlet of the recirculation loop is arranged upstream of the air intake means.

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

The production system according to the invention may further comprise fan means for extracting the exhaust gases downstream of the capture means.

The recirculation loop may advantageously include means for adjusting the recirculation flow rate, as well as fan means.

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.

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

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 means by means of a water pump. This system can be implemented in a central heating installation for a room or for heating domestic water.

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 means by means of fan means. This system can be implemented in an installation for heating the air of a room or in an installation for drying a wet product, this installation comprising a drying drum provided (i) to receive at the inlet on the one hand hot air coming from the second heat exchange means and on the other hand wet product coming from a wet product storage unit and (ii) to deliver at the outlet dried product in a recovery unit and cooled drying air.

In a third family of application of the production system according to the invention, the transfer fluid is water vapor injected into the second heat exchange means by means of a steam pump, and the production system further comprises an air recirculation loop designed to receive cooled steam from the user equipment at the inlet and inject it at the inlet of said steam pump. The production system according to the invention may further comprise surplus steam in the steam recirculation loop and be implemented in a drying installation for a wet product or in an industrial system consuming heat transported by water vapor.

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

The condensation means cooperate with means for recovering thermal energy during condensation for the purpose of recovering the fatal heat resulting from the energy conversion. The user equipment may comprise a high-pressure steam turbine driving an electricity generator.

mélanger de l’air issu d’une admission d’air et des particules métalliques issues d’une injection de particules métalliques,
injecter le mélange d’air et de particules métalliques dans un brûleur,
brûler ce mélange dans une chambre de combustion, conduisant à une production de chaleur et de gaz d’échappement,
échanger la chaleur ainsi produite, via un fluide de transfert, dans un équipement utilisateur,
capturer, à partir des gaz d’échappement, des particules oxydées en aval du brûleur,

According to another aspect of the invention, there is provided a method for producing thermal energy from a combustion of metal particles, implemented in the production system according to the invention, this method comprising the following steps:

mixing air from an air intake and metal particles from a metal particle injection,
inject the mixture of air and metal particles into a burner,
burn this mixture in a combustion chamber, leading to the production of heat and exhaust gases,
exchange the heat thus produced, via a transfer fluid, in user equipment,
capture, from the exhaust gases, oxidized particles downstream of the burner,

characterized in that it further comprises a recirculation of a first fraction of the exhaust gases, said recirculation comprising a sampling downstream of the combustion chamber and an injection of said first fraction of exhaust gas upstream of the burner means.

Exhaust gas injection can be carried out downstream of a metal particle injection, or upstream of the air intake.

DESCRIPTION OF FIGURES

Other features and advantages will appear on reading the following description of a particular, non-limiting embodiment of the invention, given with reference to the figures in which:

is a schematic representation of the water heating system of a home (sanitary and/or heating).

is a schematic representation of a home's water heating system (sanitary and/or heating) with a large exhaust gas recirculation loop.

is a schematic representation of the air heating system of a home.

is a schematic representation of the indirect hot air drying system of wet products in chemistry, construction etc.

is a schematic representation of the indirect closed loop drying system with heated steam of wet products in the chemical, construction etc.

is a schematic representation of the steam generation system for industry (brewery etc.).

is a schematic representation of the electricity generation system by a Rankine cycle (with water vapor or organic liquid called ORC).

is a schematic representation of the heat and electricity cogeneration system using a Rankine cycle and a heat recuperator placed at the condenser level to recover the fatal heat and maximize the total efficiency.

DETAILED DESCRIPTION

We will now describe, with reference to the above-mentioned figures, several examples of embodiments of energy production systems according to the invention. It should be noted that the components and modules common to the different examples illustrated have common references.

In reference to the , a thermal energy production system of the boiler/boiler room type S1 comprises an injector 100 of metal particles, a burner 3 of metal particles to be burned in a combustion chamber 4 with fixed volume, the combustion chamber 4 being connected to a suction duct 20 of a fraction 22 of exhaust gas, which is a component of a recirculation loop 20 whose reinjection outlet is arranged downstream of the particle injector 100 and upstream of the inlet of the burner 3. The other fraction 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.

The exhaust gases are composed of metal oxides and nitrogen (magnesium, iron or aluminium oxides depending on which of the three fuels is used), and pass through a filtration system 8 then a heat recovery block 1.

It should be noted that this filtration system and this heat recovery block 1 can be nested or cascaded.

The metal particle injector 100 may be in the form of a fluidization aerosol generator that injects the particles into an air flow with the help of a venturi system. It is also possible to use gravity injection of the particles using a vibrating funnel (or not) on an air line, the addition of a slight fluidization flow at the inlet of the funnel making it possible to avoid clogging the outlet. Another possibility is to use a worm screw, the diameter and rotation speed of which make it possible to control the precision and flow rate of powder injection into an air line receiving the latter.

The metal burner 4 can be produced using a " swirler " (air swirler) which makes it possible to increase the air injection flow rate without worrying about the risk of blowing out the pilot flame generated by an ignition system 2. The principle is to have part of the air flow injected axially, and another part injected tangentially using tangential tubes or static turbines, in order to create shear and recirculation zones towards the inside of the burner 3 (depression effect within the swirl generated by the centrifugal flow) and to facilitate the stabilization of the flame. Indeed, this aerodynamic stabilization mechanism makes it possible to create zones in the flow where the speeds are low enough to be close to those of the metal flames, thus ensuring that the flame clings to the burner. This mechanism is all the more important as the air load increases and the fuel concerned has relatively low flame speeds. Adjusting the intensity of the “swirl” allows you to manage the size of the flame and its overall morphology.

In order to achieve continuous stabilization of the metal flame, when using iron powder only, it is possible to preheat the combustion air entering the system. In order to reduce the use of natural gas by a pilot flame that supplements the heat released per unit volume during the combustion of iron and facilitates its ignition, it may be interesting to add a preheating block 1 of the intake air by recovering the fatal heat from the system exhaust. The iron flame is in fact more difficult to stabilize than those of magnesium or aluminum, due to its low reaction rate linked to its combustion in heterogeneous mode and the layer of oxides around the particles that greatly reduce the heat release rate and therefore the reaction temperature.

This penalizes the stabilization of the flame which is thus disturbed by losses by convection and radiation. The contribution of heat via that contained in the exhaust gases thus makes it possible to increase the overall energy efficiency, and to reduce the quantity of gas in the gas pilot flame and therefore CO2 emissions.

The intake preheating system consists of a gas-gas exchanger 1 which recovers, in the main exhaust circuit, the fatal calories to transfer them into a secondary circuit (serpentine tube, or any geometry allowing to maximize the exchange surface such as plate exchangers) to the intake air sucked in by a ventilation and which goes towards the burner for the supply of oxidant.

The pilot flame can be in the form of a methane injector 2 (or propane or butane) placed in the direction of the axial flow of iron and air, which generates a diffusion flame, or in the form of a hybrid methane/iron/air flame premixed by adding methane to the axial pipe carrying the particles in the air. A spark activated by a remote actuator can be used to 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 has been achieved thanks to their high-temperature homogeneous phase combustion which facilitates self-maintenance of the flame.

The combustion system is also optimized by the addition of exhaust gas recirculation 20, largely consisting of nitrogen, through a secondary circuit to regulate the percentage of oxygen in the mixture around the iron particles.

This secondary recirculation circuit 20 comprises a device 9 for ventilation of exhaust gas extraction and a controlled throttle valve 10 for adjusting the recirculation flow rate.

A high oxygen concentration, of the order of that of ambient air, can locally increase the reaction rate and therefore the temperature of the particles, bringing them locally above the boiling point of iron (3134 K), increasing the risk of micro-explosions of the particles (depending on the temperature and the speed of expansion of the gases formed within the particle), ultimately generating oxide nanoparticles that are very difficult to filter and regenerate into pure iron with micron particle size [ Stereoscopic high-speed imaging of iron microexplosions and nanoparticle-release, Li et al., Vol. 29, Optics Express, 2021 ].

This is problematic in the context of using iron as a circular fuel. Recirculating the exhaust gases to lower the oxygen concentration by up to 14% can significantly reduce the appearance of oxide nanoparticle clouds by reducing the reaction temperature and therefore that of the particles. The latter leads to a strong decrease in the saturation vapor pressure of the metal, 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 ].

Since oxygen concentration plays a predominant role in overall richness for fuel-lean mixtures, richness gains importance on oxygen transport and therefore on reaction temperature for richnesses closer to stoichiometry. In order to avoid deposits of unburned metal particles, an overall richness below stoichiometry is necessary. Thermal losses by radiation are also greater with the sharp increase in the temperature of these particles, which also disadvantages stabilization and causes a sharp increase in NOx emissions.

A more common effect in the context of exhaust gas recirculation applied to combustion is the reduction of thermal nitrogen oxide emissions by lowering the combustion temperature (Zeldovich mechanism).

The exhaust gas recirculation system consists of a pipe connected to the exhaust pipe, preferably downstream of the filtration, which takes the gas consisting mainly of nitrogen (and excess oxygen in the case of combustion close to stoichiometry) using an intake ventilation followed by a recirculation flow control butterfly, in order to reinject this gas upstream of the burner or directly into the intake pipe upstream of the main ventilation (in this case, thanks to the main ventilation, the intake ventilation is no longer necessary).

The recirculation rate can vary from 0 to more than 50% of the total injected flow (the reduction of NOx emissions reaches a plateau after 50% recirculation rate) and an oxygen concentration around 14% already allows to greatly reduce the phenomena of formation of oxide nanoparticles (but with this system the oxygen concentration in the intake can drop to 10%). Thus, in the context of a circular energy application, where the goal is to regenerate the initial iron particles from the oxides, the minimization of the effects producing the nanoparticle emissions allows to maintain the integrity of the particles throughout the cycle to avoid the intermediate processes of reforming the micrometric iron particles.

The means 8 for capturing oxides can consist of a set of cyclones sized to allow the filtration of oxide particles ranging from microns to several hundred microns. This is a common process in the dust removal of industrial fumes. It would also be possible to implement a sedimentation chamber that uses the inertia of large particles with a diameter of between a few microns and a few hundred microns, which, subjected to gravity, will settle at the bottom of the chamber.

The remaining nanoparticles can be filtered using a bag filter or HEPA ( High Efficiency Particulate Air ) filter, or an electrostatic or electromagnetic filter accompanied by downstream suction ventilation to overcome the pressure losses generated by all the filtration elements.

The energy production system S2 according to the invention can be used to heat the air of a home, the water of a home (sanitary and heating water) (S1), generate steam for industry (S5), dry aggregates or any wet product (S3, S4), generate electricity in a Rankine cycle using water vapor or organic liquid (S6), or co-generate heat and electricity if the heat is recovered in the condenser (S7).

The System S1 for producing thermal energy from a combustion of metal particles, comprises means 3 for burning metal particles in a combustion chamber 4, comprising an ignition system 2 provided for generating a pilot flame, means 100 for injecting metal particles into said burner means, means 5, 6 for admitting air to be injected into the burner means 3 so as to constitute a premixture of air and metal particles, comprising fan means 5 (of the blower ventilation type) and means 6 for adjusting the air intake flow rate, means for capturing the 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 provided to be injected into the heat exchange means 7 via pump means 12 and to transfer a part of combustion thermal energy in user equipment 13.

The heat exchanger 7 may be composed of a set of tubes through which the heat transfer fluid circulates, which transports the heat to the user equipment. These tubes may be located in the hot volume of the combustion chamber and the filtration or arranged around them but in contact with their walls. The heat transfer fluid is either distributed in several tubes arranged in parallel, or in a coil, with the aim of maximizing the heat exchange surface with the hot flow from the combustion chamber.

The production system S1 further comprises a recirculation loop for a fraction of the exhaust gases from the combustion chamber 4, having a gas sampling inlet downstream of the combustion chamber 4 and a gas injection outlet upstream of the burner means 3.

In reference to the , The production system S2 is a variant of the system S1, comprising a large recirculation loop 30 for a fraction of the exhaust gases from the combustion chamber 4, this large recirculation loop having a gas sampling inlet downstream of the combustion chamber 4, a gas injection outlet 32 upstream of the inlet of the ventilation means 5 for air intake, and optionally provided with a regulation unit 10.

In reference to the , the production system S3 is a variant of the system S1 for heating air by combustion of metal particles. It comprises, instead of the exchanger 13, a gas-air exchanger 13b.

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

In reference to the , the production system S5 is a variant of the production system S4, in which the transfer fluid is water vapor injected into the heat exchange exchanger 7 by means of a steam pump 12, this system further comprising an air recirculation loop 50 designed to receive at the inlet cooled steam from the user equipment 13c and inject it at the inlet of the steam pump 12.

In reference to the , the production system S6 is a variant of the embodiments of production systems S1-S4, which allows to transfer the heat of combustion to an industrial system 13d consuming heat transported by water vapor consisting of the elements of a steam generator.

In reference to the , the production system S7 is a variant of the embodiment S6, in which the transfer fluid is two-phase (i), in a liquid form upstream of the heat exchanger 7 and (ii) in a vapor form downstream of the heat exchanger 7 and at the inlet of the user equipment 17. This production system 7 further comprises a loop 70 for recovering the cooled vapor at the outlet of the user equipment 17, conducting it to the inlet of a condensation unit 18 and injecting it in liquid form into the pump means 15. The user equipment 17 includes a high-pressure steam turbine driving an electricity generator 13. The system S7 can use a Rankine cycle but also a thermodynamic converter of the Stirling type or even a converter of the external combustion gas turbine type, the combustion gas being heated by an exchanger the expansion gas which passes into the turbine, even if for applications of several MW, Rankine cycle type converters are more often found. (organic liquid or water vapor) for their economic profitability.

In reference to the , the production system S8 is a variant of the embodiment S7, in which the condensation means 14 cooperate with equipment 19, inserted in the recovery loop 70, provided for recovering thermal energy during condensation for the purposes of recovering the fatal heat resulting from the energy conversion.

Of course, the present invention is not limited to the examples that have just been described and many other embodiments can be envisaged without departing from the scope of the present invention. In particular, the on-board energy production system can be used for the propulsion of mobility systems and vehicles such as ships, railway systems, spacecraft, aircraft and in particular airships.

Furthermore, it is possible to envisage the implementation of thermal energy production systems according to the invention on the moon, by exploiting metallic particles and oxygen resulting from a process of reduction of the regolith covering its soil.

Claims

System (S1-S8) for producing 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) provided for generating a pilot flame,

means (100) for injecting metal particles into said burner means,

means (5,6) for admitting air to be injected into the burner means (3) so as to constitute a pre-mixture of air and metal particles, comprising fan means (5),

means (8) for capturing oxidized particles in the exhaust gases, downstream or combined with first heat exchange means,

first means (7) for heat exchange between a transfer fluid and the combustion chamber (4), said transfer fluid being provided to be injected into said heat exchange means (7) via pump means (12) and to transfer part of the thermal combustion energy into user equipment (13, 13b, 13c, 13d, 17),

characterized in that it further comprises a loop (20) for recirculating a first fraction (22) of the exhaust gases from the combustion chamber (4), having a gas sampling inlet downstream of the combustion chamber (4) and a gas injection outlet upstream of the burner means (3).
Production system (S1) according to the preceding claim, characterized in that the reinjection outlet of the recirculation loop is arranged downstream of the air intake means.
Production system (S1) according to the preceding claim, characterized in that the recirculation loop (20) further comprises fan means (9).
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).
Production system according to any one of the preceding claims, characterized in that the air intake means further comprise additional means (6) for adjusting the air intake flow rate.
Production system according to any one of the preceding claims, characterized in that it further comprises fan means (11) for extracting the exhaust gases downstream of the capture means.
Production system according to any one of the preceding claims, characterized in that the recirculation loop (20, 30) comprises means (10) for adjusting the recirculation flow rate.
Production system (S1-S8) according to any one of the preceding claims, characterized in that it further comprises means for preheating the intake air upstream of its injection into the burner means, said preheating means comprising second means for heat exchange (21) between a second fraction (23) of the exhaust gases from the combustion chamber and the intake air (1),
Production system (S1-S8) according to one of the preceding claims, characterized in that the first heat exchange means (7) comprise an enclosure surrounding the combustion chamber (4) and arranged to circulate the transfer fluid therein.
Production system (S1-S8) according to the preceding claim, characterized in that the heat exchange enclosure (7) also surrounds the oxide capture means (8).
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 means (7) by means of a water pump (12).
Production system (S1) according to the preceding claim, implemented in a central heating installation of a room (13).
Production system (S1) according to one of the two preceding claims, implemented in a domestic water heating installation (13).
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 means (7) by means of fan means (12).
Production system (S3) according to the preceding claim, implemented in an installation (13b) for heating the air of a room.
Production system (S4) according to claim 14, implemented in a drying installation for a wet product, said installation (13c) comprising a drying drum (14) provided (i) to receive at the inlet on the one hand hot air coming from the second heat exchange means (7) and on the other hand wet product coming from a wet product storage unit (13c) and (ii) to deliver at the outlet dried product in a recovery unit (15) and cooled drying air.
Production system (S5) according to any one of claims 1 to 10, characterized in that the transfer fluid is water vapor injected into the second heat exchange means (7) by means of a steam pump (12), and in that it further comprises a recirculation loop designed to receive at the inlet cooled steam from the user equipment (13c) and inject it at the inlet of said steam pump (12).
Production system (S5) according to the preceding claim, characterized in that it further comprises means for evacuating excess steam into the steam recirculation loop.
Production system (S5) according to one of the two preceding claims, implemented in a drying installation for a wet product.
Production system (S6) according to one of claims 17 or 18, implemented in an industrial system (13d) consuming heat transported by water vapor.
Production system (S7, S8) according to any one of claims 1 to 10, characterized in that the fluid is two-phase (i) in a liquid form upstream of the first heat exchange means (7) and (ii) in a vapor form downstream of the first heat exchange means (7) and at the inlet of the user equipment (17), and in that it further comprises means (18, 19) for condensing the cooled vapor from the user equipment (17) and injecting it in liquid form into the pump means (15).
Production system (S8) according to the preceding claim, characterized in that the condensation means (19) cooperate with means for recovering thermal energy during condensation for the purpose of recovering the fatal heat resulting from the energy conversion.
Production system (S7, S8) according to one of the two preceding claims, characterized in that the user equipment comprises a high-pressure steam turbine (17) driving an electricity generator (13e).
A method for producing thermal energy from a combustion of metal particles, implemented in the production system (S1-S7) according to any one of the preceding claims, this method comprising the following steps:

mixing air from an air intake and metal particles from a metal particle injection,

inject the mixture of air and metal particles into a burner (3),

burn this mixture in a combustion chamber (4), leading to the production of heat and exhaust gases,

exchange the heat thus produced, via a transfer fluid, in user equipment (13,13b, 13c,13d,12),

capture, from the exhaust gases, oxidized particles downstream of the burner (3),

characterized in that it further comprises a recirculation of a first fraction (22) of the exhaust gases, said recirculation comprising a sampling downstream of the combustion chamber (4) and an injection of said first fraction of exhaust gas upstream of the burner means (3).
Production method (S1) according to the preceding claim, characterized in that the injection of exhaust gas is carried out downstream of the air intake.
Production method (S2) according to claim 24, characterized in that the injection of exhaust gas is carried out upstream of the air intake.