Apparatus for the production of hydrogen and related process

Abstract

Apparatus (100) for the production of hydrogen by means of electrolysis of water, comprising a central body (120) consisting of a refractory chamber and comprising: a first zone (101) comprising a burner; a second zone (102) directly connected with the first zone (101) and arranged downstream of the latter, provided with devices (111) for controlling the temperature of the combusted gas exiting from said first zone and for regulating and delivering a coolant; and a third zone (103), directly connected with the second zone (102), comprising a high-temperature solid oxide electrolytic cell (SOEC), said apparatus (100) further comprising: upstream of the central body (120) at least one supply line (104), (105) and (106) for respectively supplying at least one fuel; oxygen and a diluent, and directly connected with the third zone (103) of the central body: an outlet line (107), and (108) for hydrogen and any carbonaceous combusted gases; and oxygen.

Description

[0001] TITLE: “Apparatus for the production of hydrogen and related process" DESCRIPTION FIELD OF THE INVENTION

[0002] The present invention is in the field of apparatuses and processes for the electrolytic production of hydrogen by means of SOEC and in particular for the production of green hydrogen.

[0003] STATE OF THE ART

[0004] The interest in the electrolysis of water and the production of so-called green hydrogen, i.e., obtained through processes that as a whole do not lead to a net production of CO2, is in continuous and constant increase. However, this electrolysis process is particularly onerous today from an energy point of view, with an electrical requirement of about 55 kWh to produce 1 kg of green hydrogen (Hillestad et al., 2018). The most widely used systems currently are electrolysis cells, predominantly alkaline (so-called AEC) or membrane (so-called PEM) cells. However, a third family of electrolyzers also exists, which is more efficient but not yet commercialized on a large scale: the solid oxide cells (so-called SOEC). SOECs, like the other AEC and PEM systems, allow to obtain hydrogen - and therefore oxygen in appropriate stoichiometry -according to the reaction:

[0005] [Rl]: H2O = H2+ ’ O2

[0006] but at a considerably lower cost. In Figure la), the graph is shown (Hillestad et al., 2018) according to which an appropriate operation with SOEC would lead to a theoretical electrical energy consumption equal to about half of that required by AEC and PEM systems, or just over 28 kWh / kg of hydrogen. In practice, this consumption must be increased by only about 20% taking into account the high conversion efficiency of SOECs.

[0007] Problem of the known art

[0008] However, in order to ensure sufficient mobility of the oxide ions within the solid oxide interposed between the anode and cathode of the SOEC, the operating conditions require high temperatures. For this reason, the problem arises from the fact that to theaforementioned electrical energy cost must be added the energy expenditure required for the production of high-temperature steam (Figure la), 830°C).

[0009] Furthermore, having as its purpose the production of green hydrogen, said steam must be produced without the aid of systems that generate net CO2 emissions (such as, for example, combustions in furnaces), but rather by exploiting electrified processes and preferably supplied by renewable energy sources (solar, wind, geothermal, nuclear, biomass, etc...).

[0010] The energy cost to produce said high-temperature steam, even using renewable energy, is in any case extremely high and some equipment is subject to rapid degradation. Typically, the generation of high-temperature steam occurs in 4 phases (Figure lb)): 1. Heating of the water from the initial temperature (for example, ambient temperature) up to the temperature close to the boiling conditions (for example, 95°C, 1 atm) by means of a recuperator, consisting of a liquid / liquid heat exchanger (typical heat exchange coefficient: 0.6 kW / m2 / K);

[0011] 2. Disengagement of the generated saturated steam (boiling temperature, for example 100°C at 1 atm) by means of a boiler consisting of a unit usually equipped with a tube bundle for heat exchange and a vessel for it. Usually, the boiler is of the kettle or calandria type (McCabe et al., 2005) and is a liquid / boiling heat exchanger (typical heat exchange coefficient: 1.1 kW / m2 / K).

[0012] 3. First stage of superheating of the steam (for example from 100°C to 500°C) carried out by means of a first superheater, generally consisting of a gas / gas tube bundle heat exchanger (typical heat exchange coefficient: 0.2 kW / m2 / K).

[0013] 4. Second stage of superheating of the steam (for example from 500°C to 830°C) generally carried out by means of a second superheater, consisting of a gas / gas tube bundle heat exchanger (typical heat exchange coefficient: 0.2 kW / m2 / K).

[0014] The above-mentioned apparatuses can be replaced by a furnace (without emissions), thermal or electric, but the efficiency is not significantly different.

[0015] For example, US20180287179 Al discloses a method for heat management in SOEC, SOFC (Solid Oxide Fuel Cell) and / or rSOC (reversible Solid Oxide Cell) systems that allows recovering the heat of the gaseous effluents of said systems by means of heatexchangers in order to produce the steam required by the electrolytic reaction, which however requires, at least initially, an external heat source to reach the operating temperature.

[0016] CN117051411 A describes a system for the production of hydrogen by means of SOEC in which the steam used as a reactant must be formed by means of a steam generator from condensed water, possibly recovered from the unreacted steam in the SOEC, recovering the heat from the effluents of the electrolytic cell, in the presence of a heater necessary for the control and reaching of the operating temperatures of the SOEC. US20150368818 describes the use of heating units useful for reaching the operating temperatures of the SOEC in mechanical contact with the stacks that make up the SOEC, constituting integrated parts directly in the stacks. Said heating units can be electrical resistances or chemical heaters in which the heat, transmitted to the SOEC by convection, develops following the combustion of a fuel and one of the process gases produced by electrolysis (H2 or 02).

[0017] US11769890 discloses an SOEC system in which pressure and / or mass control systems are exploited to balance the flow of a supply gas that does not actively take part in the reactions in the SOEC (e.g., CO2), in order to improve the controllability of the ejector of an SOEC system, without however directly acting on the energy efficiency of the system.

[0018] The problem of energy efficiency, and particularly of heat management, of systems that integrate SOEC for the production of hydrogen, preferably by means of economical and compact apparatuses and even more preferably integrated into processes that do not provide for net CO2 emissions, is therefore particularly felt. SUMMARY OF THE INVENTION

[0019] The object of the invention is an apparatus for the production of hydrogen by means of electrolysis of water, comprising a central body consisting of a refractory chamber and comprising:

[0020] - a first zone comprising or consisting of a burner, in which the combustion between said fuel and oxygen occurs;- an optional second zone, directly connected with the first zone and arranged downstream of the latter, said second zone being provided with devices for controlling the temperature of the combusted gas exiting from said first zone and for regulating and delivering a coolant to cool the combusted gases exiting from said first zone, said devices being able to regulate the flow rate of coolant to be flowed into said second zone as a function of the temperature reached by the combusted gases exiting from said first zone; and

[0021] - a third zone, directly connected with the first zone or with the second zone, when the latter is present, said third zone comprising or consisting of a high-temperature solid oxide electrolytic cell (SOEC),

[0022] said apparatus further comprising:

[0023] - upstream of said central body at least one supply line for supplying respectively and separately or in premixing the following compounds:

[0024] Al) at least one fuel;

[0025] A2) oxygen and

[0026] A3) a diluent

[0027] - and directly connected with the third zone of the central body: B) an outlet line, and for each of the following compounds produced in the central body:

[0028] Bl) hydrogen, any carbonaceous combusted gases and any residual steam;

[0029] B2) oxygen and any residual steam.

[0030] A further object of the present invention is a process for the production of hydrogen comprising:

[0031] a) burning a fuel selected from hydrogen, a C1-C5 hydrocarbon or mixtures thereof, in the presence of oxygen and a diluent,

[0032] b) optionally cooling the combusted gas and the diluent coming from step a) by delivering a flow rate of a coolant as a function of the temperature at the outlet of step a);c) carrying out the electrolysis of water in a solid oxide electrolytic cell (SOEC) on the combusted gas coming from step a) or b) according to the reaction:

[0033] [Rl]: H2O = H2 + ' / 202;

[0034] said process being conducted in the apparatus wherein step a) is conducted in the first zone of the central body; the optional step b) of optional cooling of the combusted gases is conducted in the second zone of the central body and step c) is conducted in the third zone of the central body.

[0035] Advantages of the invention

[0036] With the apparatus object of the present invention and the related process for the electrolytic production of hydrogen by means of SOEC carried out in said apparatus, it is possible to reduce the energy operating costs, particularly in terms of electrical energy.

[0037] The apparatus and the related process of the invention are characterized by the following main advantages with respect to the known art:

[0038] • it is possible to produce hydrogen and optionally also oxygen by electrolysis with a lower energy consumption, thus making the production of green hydrogen more accessible, also given the lower requirement for energy integration through renewable sources;

[0039] • the temperature control allows to obtain a higher performance of the SOEC cells, both with respect to all other types of electrolytic cells, and with respect to standard SOEC systems; the same temperature control guarantees to reduce the degradation of the electrolytic cells, guaranteeing operation at optimal temperatures, increasing the precision and durability of operation;

[0040] • the conformation of the apparatus of the present invention is endowed with lower constructional complexity; the apparatus is therefore simpler as a whole from a mechanical, electronic, automation and control point of view;

[0041] • the process is characterized by greater controllability and operational flexibility, due, for example, to the fact that heating, steam generation and superheating systems are not necessary, leading as a whole to a simplification of the process and control;• the apparatus of the present invention is easily modular by introducing, according to some preferred alternatives, units capable of guaranteeing the energy selfsustainability of the system, comprising, for illustrative purposes only, photovoltaic panels, tanks for rainwater collection, anaerobic digesters;

[0042] • according to preferred alternatives, the apparatus can be equipped with units that allow the distributed production of e-fuels, i.e., also carbonaceous fuels obtained through processes without net CO2 emissions via an electrochemical route;

[0043] • the advantages mentioned above allow as a whole a reduction of CAPEX and OPEX.

[0044] DESCRIPTION OF THE FIGURES

[0045] Figure la) shows a graph in which on the left ordinates the power measured in kWh / kg of H2 produced is reported, on the abscissas the outlet temperature of the SOEC is reported and on the right ordinates the inlet temperatures from the SOEC; x is the molar fraction of the steam converted after electrolysis. Figure lb) shows a process scheme of a conventional train of heat exchangers for the generation of high-temperature steam.

[0046] Figure 2 represents a preferred embodiment of the apparatus of the present invention in which the zone of the apparatus is provided with devices for cooling and controlling the temperature of the combusted gases exiting from the first zone.

[0047] Figure 3 represents a preferred embodiment of the apparatus of Figure 2 of the present invention, in which the totality of the oxygen production is recycled for selfconsumption.

[0048] Figure 4 represents a further preferred embodiment of the apparatus of Figure 2, in which only a part of the oxygen production is recycled for self-consumption, while the remaining part can be conveyed externally to the central body of the apparatus.

[0049] Figure 5 represents a further embodiment of the apparatus of Figure 2, in which a part of the produced hydrogen is recycled for self-consumption.

[0050] Figure 6 shows a flow diagram of the process according to the present invention conducted in the embodiment of Figure 5 in which: CRV-100 represents the first zone (101) and the second zone (102); CRV-101 and X-100 represent the third zone (103);V-100 and X-101 represent units that are not part of the present invention for the recycling of streams.

[0051] Figure 7 represents a further embodiment of the apparatus of Figure 4, in which the fuel used is methane.

[0052] Figure 8 shows a flow diagram of the process according to the present invention of the apparatus of Figure 7 in which CRV-100 represents the first zone (101) and the second zone (102); CRV-101 and X-100 represent the third zone (103); V-100 and X-101 represent units that are not part of the present invention for the recycling of streams. Figure 9a) shows a preferred embodiment of the apparatus of Figure 4 inserted in a process for the production of conditioned syngas. Figure 9b) represents a flow diagram of the process according to the present invention conducted in the embodiment of the apparatus of Figure 9a) in which CRV-100 represents the first zone (101) and the second zone (102); CRV-101 and X-100 represent the third zone (103); V-100 and X-101 represent units that are not part of the present invention for the recycling of streams.

[0053] Figure 10a) shows an embodiment in which the apparatus of Figure 4 is inserted in a process for the production of e-fuels and e-chemicals, in other words high value-added chemical products obtained via an electrochemical route. Figure 10b) represents a flow diagram of the process conducted in the apparatus according to the embodiment of the present invention represented in Figure 10a) in which e-methanol is produced and in which CRV-100 represents the first zone (101) and the second zone (102); CRV-101 and X-100 represent the third zone (103); V-100 and X-101 represent units that are not part of the present invention for the recycling of streams.

[0054] Figure 10c) shows a flow diagram of the process conducted in the plant of Figure 10a) in which a reverse water gas shift unit (GBR- 100) is present for the production of e-methanol and in which CRV-100 represents the first zone (101) and the second zone (102); CRV-101 and X-100 represent the third zone (103); V-100 and X-101 represent units that are not part of the present invention for the recycling of streams.

[0055] Figure Ila) represents an embodiment of the apparatus according to the present invention, in which the fuel used is methane and the thermal diluent comprises CO2.Figure 11b) represents an apparatus according to an embodiment of the present invention, in which the recycle lines for the self-consumption of hydrogen and / or oxygen are internal to the central body (120).

[0056] Figure 12a) represents an apparatus of Figure 2, comprising a photovoltaic plant for the electrical supply.

[0057] Figure 12b) represents the embodiment shown comprising, in addition to the photovoltaic plant, a rainwater filtration and storage system.

[0058] Figure 12c) represents the embodiment shown in Figure 12b) comprising a photovoltaic plant and a water recovery unit and applied in the production of e-fuels. Figure 13a) represents an embodiment in which methane is fed as an exogenous fuel to the apparatus connected upstream with a photovoltaic plant and a rainwater filtration and storage system.

[0059] Figure 13b) represents the embodiment shown in Figure 13a) in which e-fuels are produced.

[0060] Figure 13c) represents the embodiment shown in Figure 13b) in which biogas from an anaerobic digester is fed for the production of e-bio-fuels.

[0061] DETAILED DESCRIPTION OF THE INVENTION

[0062] For the purposes of the present invention, the definition “comprising” does not exclude the presence of further components / steps, in addition to those expressly listed after said definition.

[0063] For the purposes of the present invention, the definitions “consisting in” or “consisting of’ instead exclude the presence of components / steps not expressly listed.

[0064] For the purposes of the present invention, “refractory chamber” is intended as a chamber consisting of or comprising refractory material. In the case where the chamber comprises the refractory material, the latter is arranged inside said chamber, in direct contact with the high-temperature gases.

[0065] For the purposes of the present invention, “diluent” is intended as a fluid that is added to the products of the combustion reaction, possibly allowing a first cooling of said products.Preferably, the diluent is selected from the group consisting of: water, CO2, and combinations thereof.

[0066] For the purposes of the present invention, “coolant” is intended as a fluid that, added to and placed in direct contact with the products of the combustion reaction and the diluent, lowers their temperature.

[0067] Preferably, the coolant is selected from water, CO2, and combinations thereof.

[0068] For the purposes of the present invention, “fuel” is intended as a substance capable of reacting with oxygen in a combustion reaction producing water.

[0069] Preferably, the fuel is selected from the group consisting of: hydrogen, a C1-C5 hydrocarbon, and combinations thereof, preferably hydrogen or methane.

[0070] Preferably, the combustion reaction is complete, i.e., for example in the case where the fuel is a hydrocarbon, the combustion products are water and carbon dioxide. In other words, preferably the combustion reaction is not partial, i.e., it does not lead to the formation of compounds in intermediate oxidation states, as for example in the case of the partial combustion of hydrocarbons which leads to the formation of carbon monoxide.

[0071] Advantageously, the apparatus object of the present invention allows producing hydrogen by means of electrolysis of water with better operating performance and easier management and construction.

[0072] According to an embodiment of the apparatus according to the present invention, the second zone of the central body may not be present; in this case the cooling action on the combusted gases is exerted only by the diluent.

[0073] In any case, the preferred embodiment of the apparatus object of the present invention is that which provides for the second zone arranged between the first zone, where the combustion reaction occurs, and the third zone, comprising or consisting of the solid oxide electrolytic cell. The second zone is therefore provided with devices and systems for controlling the temperature of the gas exiting from said first zone and for regulating the delivery of the coolant according to the temperature of the combusted gases exiting from said first zone.According to another embodiment of the apparatus object of the present invention, the outlet line for the oxygen produced in the third zone of the central body is connected via a recycle line to the oxygen supply line entering the central body and optionally with an outlet line to convey the produced oxygen externally to said central body. Said oxygen recycle line further comprises all the units known to the person skilled in the art possibly useful for its optimal operation, such as, for illustrative purposes only, blowing units, filters, separation / purification units for undesired components of the gaseous stream.

[0074] According to another preferred embodiment, the oxygen outlet line is connected only with the recycle line.

[0075] According to another embodiment of the apparatus according to the present invention, the oxygen outlet line and the recycle line are internal to the central body.

[0076] According to a preferred embodiment of the plant according to the present invention, the apparatus object of the present invention comprises an outlet and recycle line for hydrogen connected to the fuel supply line entering the first zone of the central body. Said hydrogen recycle line further comprises all the units known to the person skilled in the art possibly useful for its optimal operation, such as, for illustrative purposes only, blowing units, filters, separation / purification units for undesired components of the gaseous stream.

[0077] Preferably, the hydrogen outlet and recycle line is internal to the central body.

[0078] A further object of the present invention is a process for the production of hydrogen conducted in the apparatus reported above.

[0079] Preferably, when the process according to the present invention provides for the use of methane as a fuel, which is blown through the inlet, together with the oxygen through the inlet, and with the diluent preferably selected from water and carbon dioxide through the inlet into the first zone of the central body where step a) is conducted, where CO2 and steam are formed according to the reaction:

[0080] [R3] : CH4+ 2 O2= CO2 + 2 H2OThe products obtained in the aforesaid reaction and the diluent are optionally cooled in the optional second zone; the cooled combusted gases, obtained in step b) and coming from the second zone or the combusted gases obtained in step a) and coming from the first zone, when the second zone is absent, enter the third zone where step c) of electrolysis in a solid oxide cell is conducted; the humid hydrogen obtained in the third zone exits the central body from the outlet line dedicated to it together with the CO2, produced in step a) while the oxygen exits the central body through the outlet dedicated to it.

[0081] More preferably, said process provides that, when the fuel is methane, the apparatus provides for the second zone in which the CO2 and the steam exiting from the first zone, which have a temperature lower than or equal to 1500°C, are cooled to a temperature lower than 1000°C, preferably lower than 900°C and more preferably ranging between 700 and 900°C, before entering the third zone where step c) is conducted.

[0082] Preferably, when the fuel is hydrogen, it is blown through the inlet line dedicated to it together with the oxygen through the inlet line dedicated to it and with the diluent selected from water and CO2 through the inlet line dedicated to it in the first zone of the central body where step a) is conducted and where steam is formed according to the reaction:

[0083] [R2]: H2+1 / 2O2= H2O

[0084] Preferably, the steam exits the first zone of the central body in thermal equilibrium with the effluents, i.e., at a temperature lower than or equal to 1500°C and is cooled in the second zone to a temperature lower than 1000°C, preferably lower than 900°C and more preferably at a temperature ranging between 700 and 900°C before entering the third zone, in which the electrolysis reaction is conducted and through the outlet dedicated to it only humid hydrogen exits, while the oxygen exits the central body through the outlet dedicated to it.

[0085] According to a preferred alternative of the process of the invention, the oxygen produced in step c) exiting from the third zone of the central body is conveyed into the outlet connected only to a recycle line connected to the oxygen inlet line in the first zone of the central body.According to another preferred alternative of the process of the invention, the oxygen produced in step c) exits from the third zone of the central body through the outlet dedicated to it and is partly recycled via the said recycle line and introduced via the inlet line dedicated to it into the central body in the first zone and partly exits from the central body) through the outlet dedicated to it by means of the line which is also connected with the said outlet line).

[0086] Preferably, part of the hydrogen produced in step c) in the third zone of the central body is recycled via a further line and enters the first zone of the central body.

[0087] In Figure 2, an embodiment of the apparatus object of the present invention is shown. In it, particularly in the apparatus 100, the central body 120 consists of a refractory chamber comprising: a first zone 101 of oxidation in which the combustion (exothermic) of the fuel is carried out, generating heat, possibly already mitigated, even if only partially, by injection of diluent; a second zone 102 in which the combusted gases are cooled by delivery of a coolant, which is supplied as a function of the temperature of the combusted gases exiting from the first zone 101 and finally a third zone 103 in which the reaction [Rl] is carried out at high temperature by means of SOEC-type electrolyzers.

[0088] The fuel that enters the first zone 101 of the central body 120 via the line 104 is mixed with the oxygen, which enters the same zone via the line 105, and together with the diluent, specifically water, via the inlet line 106. The amount of oxygen must be such as to allow the oxidation reaction within the first zone 101 (at least 20% of the stoichiometric amount of the fuel added to the 100% stoichiometry of the fuel) with respect to the stoichiometric amount of the fuel and more preferably in slight excess (e.g. at least 102%) with respect to the stoichiometric amount of fuel to ensure its complete combustion.

[0089] In these cases, the first zone 101 of the apparatus reaches the adiabatic flame temperature (even higher than 3000 K) and it is therefore necessary to supply the thermal diluent via the line 106.

[0090] It is particularly advantageous to supply water or low-temperature steam as a coolant in the quantities necessary to reach the desired temperatures in the effluents of the first zone, at temperatures preferably ranging between 800 °C and 1000 °C.By means of the apparatus object of the present invention, it is possible to supply the coolant, preferably water, only partially in the first zone 101 via the inlet 106 and complete the supply in the second zone 102 where the precision control of the temperature is carried out, by adequately dosing by means of spray or injection through the devices 111 the exact amount of water / steam to correct the temperature of the effluents before they reach the third zone 103.

[0091] In the third zone 103, the electrolysis takes place at optimal conditions, suitably guaranteed by the second zone 102, for the production of pure hydrogen and oxygen. According to what is illustrated in Figure 1, it is possible to choose the inlet temperature to the third zone 103 and the outlet temperature from the third zone 103 and, therefore, the efficiency of the SOEC as a whole, which can therefore also be optimized in terms of energy expenditure.

[0092] The hydrogen produced by electrolysis exits the central body 120 via the outlet 107, while the oxygen exits the central body via the outlet 108.

[0093] In Figure 3, an embodiment of the apparatus described in Figure 2 is shown, in which the apparatus 100 allows producing the totality of the oxygen necessary for its operation, operating in self-consumption of oxygen, or overproducing it (Figure 4), depending on which fuel is used and the quantity and nature of the introduced coolant. In Figure 3, the oxygen produced in the central body 120 via the said outlet 108 is only connected with the recycle line 109 which conveys all the produced oxygen to the inlet line 105 which introduces it into the first zone 101 of the central body 120.

[0094] In the embodiment of Figure 4, instead, the apparatus 100 provides for an energy selfefficiency through the partial consumption of produced hydrogen (shortly after its ignition) and optionally of the required stoichiometric oxygen.

[0095] In Figure 6, the flow diagram of the process conducted according to this last preferred embodiment is shown by means of detailed simulation carried out with the aid of consolidated process suites (e.g. Unisim Design, AspenHysys, PRO / II), while in Example 1 the respective mass and energy balances are reported.Again according to what is reported in Example 1, the apparatus 100 is more attractive for CAPEX and OPEX having a yield higher by 41.26% with respect to SOECs with steam generation, considered the most efficient class of electrolyzers.

[0096] Preferably, the water fed as coolant from the inlets 106 and 111 can be pumped in the liquid phase at pressures preferably higher than 5 atm, more preferably higher than 10 atm, even more preferably higher than 15 atm, however compatible with the SOEC electrolyzers, saving the typically much higher costs of vapor phase compression. In this case, the apparatus achieves efficiencies that are even double compared to conventional systems that provide for the production and storage of green hydrogen. According to a preferred alternative, the operation of the apparatus provides for a supply of hydrogen with a flow rate ranging between 0.5 and 2 kmol / h, preferably 1 kmol / h (2.02 kg / h) and a supply of oxygen with a flow rate ranging between 0.25 and 1 kmol / h, preferably 0.5 kmol / h of oxygen (16 kg / h).

[0097] According to this preferred alternative, a flow rate of diluent, preferably water, ranging between 140 and 180 kg / h, preferably 158 kg / h, is supplied to the first zone and a flow rate of coolant, preferably water, ranging between 10 and 30 kg / h, preferably 18 kg / h to the second zone. Preferably, the coolant and the diluent are both at a temperature ranging between 10 and 30 °C, preferably 25 °C. Preferably, the flow rates of coolant and diluent comprise a quantity ranging between 20 and 40%, preferably 27%, of coolant and diluent respectively, preferably water, from recycle after start-up. Preferably, the effluent exiting the second zone is at a temperature ranging between 800 and 900 °C, preferably 850 °C.

[0098] Preferably, the apparatus 100 can be fed with fuels other than hydrogen. In the preferred embodiment of Figure 7, which represents a preferred embodiment of the apparatus of Figure 4, the use of methane as a fuel in oxy-combustion with selfgenerated stoichiometric oxygen and temperature mitigation by supplying water as a diluent through the inlet line 106 is reported.

[0099] In Figure 8, the flow diagram of the process conducted in the apparatus of Figure 7 is shown, by means of detailed simulation carried out with the aid of consolidated process suites (e.g. Unisim Design, AspenHysys, PRO / II), while in Example 2 the respective mass and energy balances are reported.According to a preferred alternative, the operation of the apparatus provides for a supply of methane with a flow rate ranging between 0.5 and 2 kmol / h, preferably 1 kmol / h (16 kg / h) and a supply of oxygen with a flow rate ranging between 1 and 4 kmol / h, preferably 2 kmol / h of oxygen (64 kg / h).

[0100] According to this preferred alternative, a flow rate of diluent, preferably water, ranging between 140 and 180 kg / h, preferably 162 kg / h, is supplied to the first zone and a flow rate of coolant, preferably water, ranging between 10 and 30 kg / h, preferably 18 kg / h to the second zone. Preferably, the coolant and the diluent are both at a temperature ranging between 10 and 30 °C, preferably 25 °C. Preferably, the flow rates of coolant and diluent comprise a quantity ranging between 20 and 40%, preferably 27%, of coolant and diluent respectively, preferably water, from recycle after start-up. Preferably, the effluent exiting the second zone is at a temperature ranging between 800 and 900 °C, preferably 850 °C.

[0101] The efficiency of the apparatus 100 according to Example 2 is even higher than the implementation mode shown in Example 1 as it has no internal self-consumption of hydrogen.

[0102] However, the alternative described above and illustrated in Figures 7 and 8 and in Example 2 produces CO2 due to the oxidation of the methane used as fuel. This methane can be of fossil origin and released into the atmosphere. In this case, this implementation mode leads to the production of LCF (Low Carbon Fuel) hydrogen having a significantly lower environmental impact than traditional steam methane reformer units (Vita et al. 2018; Quirino et al., 2020, 2022). For each kg / h of hydrogen produced according to this alternative, 2.47 kg / h of CO2 are also produced.

[0103] A traditional steam reformer complete with a shift system, on the contrary, operates according to the following reactions:

[0104] [R4] CH4+ H2O = CO + 3 H2

[0105] [R5] CO + H2O = CO2+ H2

[0106] which overall lead to the overall reaction:

[0107] [R6] CH4+ 2 H2O = CO2+ 4 H2In accordance with reaction [R6] alone, for each kg / h of hydrogen produced by steam methane reforming, 5.5 kg / h of CO2 are produced, well over double that produced by this preferred alternative. However, to the CO2 production of a steam methane reformer must also be added the CO2 production on the burner side (fire box), which provides for a combustion (in air) of methane according to the stoichiometry of reaction [R3] with a further increase in the environmental impact up to 7 kg / h of CO2 per kg / h of hydrogen produced. Finally, with the various inefficiencies of combustion and heat exchange, the impact of a typical reformer unit can reach (and exceed) even 10 kg / h of CO2 per kg / h of hydrogen produced.

[0108] Preferably, in the case where the fuel comprises or consists of methane, other hydrocarbons or other carbonaceous fuels, the apparatus 100 may provide for a downstream recovery of CO2 known to the expert. In this case, classic systems such as Pressure Swing Adsorption, amine mixtures in absorption / regeneration columns, membranes, molecular sieves can be used, more preferably, since the stream is contaminated only by CO2, fully electrified recovery systems that use only water (such as, for example, PSWA or Pressure Swing Water Absorption, WO2022 / 234430 Al). Preferably, the methane used as fuel can be of biogenic origin.

[0109] Preferably, the apparatus 100 can provide for a partial self-consumption of hydrogen even in the co-presence of other fuels.

[0110] According to a preferred modality, the apparatus 100 can be connected to a production unit of conditioned green syngas downstream of said apparatus of Figure 4 with partial self-consumption of oxygen.

[0111] The syngas production unit can possibly be preceded by a dehydration unit (Dewatering) and the condensed water is recycled to the inlet 106; the syngas production unit allows consuming exogenous CO2 from any source (bio or fossil), such as for example cement plants, steel plants, hard-to-abate systems in general. By conditioned syngas is meant a H2 / CO / CO2 mixture such that the synthesis ratio SN as reported in the literature (Bozzano and Manenti, 2016) is:

[0112] SN = (H2 - CO2) / (CO + CO2) = 2i.e., the optimal value for organic syntheses. In Figure 9b) a flow diagram of the process conducted in the plant of Figure 9a) is illustrated, while in Example 3 the respective mass and energy balances are reported.

[0113] According to further preferred embodiments schematically represented in Figure 10a), the apparatus 100 according to the present invention can be connected downstream to a synthesis unit for e-fuels and / or e-chemicals. Also in this case, the said synthesis unit can be preceded by a dehydration unit. This synthesis unit allows carrying out, for example, Fisher-Tropsch reactions for the production of synthetic fuels defined in the figure as e-fuels, the synthesis of methanol which falls within the class indicated in the figure as e-chemical, the synthesis of e-DME which falls within the class of fuels defined in the figure as e-fuel, the synthesis of kerosene (SAF, sustainable aviation fuel), also falling within the class of e-fuels, the synthesis of olefins that can fall into the category of e-chemicals and e-fuels and methane by Sabatier reaction. In Figure 10b) the relative flow diagram of the process conducted in the plant of Figure 10a) is illustrated, in which the synthesis unit is dedicated to the synthesis of methanol, while in Example 4 the respective mass and energy balances are reported.

[0114] According to another embodiment reported in Figure 10c), the plant of Figure 10a) comprises a reverse water gas shift unit (as per the reverse reaction of [R5]) downstream of the apparatus according to the present invention, and upstream of the optional dehydration unit and the synthesis unit. In this way, it is possible to generate CO from the CO2 present in the effluents of the found to make the organic syntheses downstream of the found more efficient;

[0115] Preferably, the coolant comprises or consists of water and / or CO2 (as reported in the embodiment Ila)). For example, the use of CO2 or other substances as coolant is provided suitably combined with the amount of steam to be supplied, preferably where the injection of the said coolant is useful for the subsequent operations / reactions. Preferably, the apparatus 100 comprises one or more internal recycles in cases of selfconsumption of hydrogen and / or oxygen (Figure 11b)). To this end, at least one blowing / compression unit for the recycle may be necessary.

[0116] According to a preferred embodiment reported in Figure 12a), the apparatus 100 can be connected upstream with systems for the production of renewable energy for totalor partial energy self-sustainability. Preferably, the apparatus comprises a photovoltaic area of an extension sized according to the energy requirement (as shown in the energy balances reported in the examples) suitably positioned above or upstream of the apparatus to be invested by solar rays. Preferably, the capacity must be such as to contain the solution in one or more skids.

[0117] According to a further preferred alternative described in Figure 12b), the apparatus 100 is connected to a rainwater storage unit and pipelines and filtration systems for the collection of rainwater. When this alternative also comprises systems for the production of renewable energy such as photovoltaic systems for energy supply, the apparatus is totally sustainable in its modes of self-consumption of hydrogen except for periods of lack of precipitation, making it totally disconnected from any supply line after its initial activation. In case of water shortage, it is possible to supply the tank (internal or external) artificially. A qualitative scheme of this alternative is reported in Figure 13b).

[0118] According to the embodiment described in Figure 12c), the apparatus 100 connected to systems for the production of renewable energy and to a rainwater storage unit receives CO2 for the production of conditioned syngas. The CO2 can be supplied via connection with external supply, via cylinder / storage also contained inside or by means of capture systems, adjacent if in proximity to CO2 sources, or from the air by means of Direct Air Capture (DAC) techniques. The installation of this modality in proximity to the use of the syngas is preferable.

[0119] Preferably, the apparatus 100 connected to systems for the production of renewable energy and to a rainwater storage unit can be fed with a fuel other than hydrogen, preferably methane, with production of CO2 that can be released into the atmosphere or stored or even sent in line to other handling / storage / use systems (Figure 13a)). Alternatively, the CO2 is consumed directly downstream for the production or coproduction of e-fuels or other compounds. In this case, the CO2 can also be integrated with an additional feedstock (Figure 13b)).

[0120] Preferably, the fuel can come from the grid, from direct production, from external storage (cylinders or tanks), from internal storage.Preferably, the apparatus 100 is integrated with oil wells, refineries, cement plants, steel plants and hard-to-abate systems for the supply of methane or CO2.

[0121] According to a preferred alternative, the apparatus 100 is integrated with an anaerobic digester (Figure 13c)), possibly comprising systems for the production of renewable energy and a rainwater storage unit, to produce e-bio-syngas and favor any type of carbon negative synthesis (for example, Fisher-Tropsch, methanol, Sabatier, hydrogenation). In this case, an additional supply of CO2 from the outside is possible. In particular, for each kg / h of classic biogas (60 %v / v methane and 40%v / v CO2) it is possible to provide for the supply of at least 1 kg / h of exogenous CO2.

[0122] Preferably, the apparatus comprises a fuel pump downstream, in proximity to or even part of the apparatus according to the present invention.

[0123] EXAMPLES

[0124] Hereinafter, the Applicant provides some examples for illustrative and non-limiting purposes.

[0125] Example 1: Apparatus with partial self-consumption of hydrogen

[0126] According to the preferred alternative described in Figures 5 and 6, i.e., according to the preferred alternative with partial self-consumption of hydrogen, the operation of the apparatus provides for a supply of 1 kmol / h of hydrogen (2.02 kg / h) and 0.5 kmol / h of oxygen (16 kg / h), according to the stoichiometry of the oxy-combustion reaction of hydrogen:

[0127] [R2] H2+ U O2= H2O

[0128] Under these conditions, it is appropriate to supply 180 kg / h of water (of which 49 kg / h from recycle after start-up) at a temperature of 25°C between the first zone (101) and the second zone (102), for example 90% to the first zone and 10% to the second zone, of the found to obtain an effluent at the outlet at 850°C. The effluent at the outlet is pure steam (with possible traces of oxygen and / or hydrogen) at the optimal operating temperature of the SOEC. 116.4 kg / h of pure oxygen are obtained, net of the 16 kg / h in self-consumption, and 14.67 kg / h of hydrogen net of the 2.02 kg / h in selfconsumption and following a dehydration (the recovery water is recycled upstream). The energy expenditure of the found is equal to 522 kWh, i.e., 35.58 kWh per kg ofhydrogen. Compared to traditional electrolysis techniques (55 kWh per kg of hydrogen), the efficiency is significantly higher. If compared to the efficiency of an SOEC where it is necessary to produce high-temperature steam according to the conventional method of Figure 2 by supplying power, the efficiency is equal to 50.26 kWh per kg of hydrogen, still significantly far from the 35.58 kWh per kg of hydrogen of the found, by virtue of the autothermicity of the refractory chamber.

[0129] Example 2: Apparatus with consumption of methane as fuel

[0130] According to the preferred alternative described in Figures 7 and 8, i.e., according to the implementation modality in which there is consumption of methane as fuel, the operation of the apparatus provides for a supply of 1 kmol / h of methane (16 kg / h) and 2 kmol / h of oxygen (64 kg / h), according to the stoichiometry of the oxy-combustion reaction of methane:

[0131] [R3] CH4+ 2 O2= CO2 + 2 H2O

[0132] Under these conditions, it is appropriate to supply 176 kg / h of water (of which 49 kg / h from recycle after start-up) at a temperature of 25°C between zone 1 and zone 2 of the found, for example 90% to the first zone and the remaining 10% to the second zone, to obtain an effluent at the outlet at 850°C. The effluent at the outlet is predominantly steam (92.17% v / v) in co-presence of a minimal part of CO2 (7.83% v / v) with possible traces of oxygen and / or hydrogen at the optimal operating temperature of the SOEC. The presence of a small part of CO2 in the steam stream requires a tolerant solid oxide known to the expert. 77.2 kg / h of pure oxygen are obtained, net of the 64 kg / h in selfconsumption, 17.79 kg / h of hydrogen following a dehydration (the recovery water is recycled upstream) and 44 kg / h of humid CO2 (with 4 kg / h of water). The energy expenditure of the found is equal to 576 kWh, i.e., 32.38 kWh per kg of hydrogen. This efficiency is even higher than the implementation modality described in Example 1, as the internal self-consumption of hydrogen is not present.

[0133] Example 3: Apparatus for the production of conditioned syngas

[0134] According to the preferred alternative described in Figures 9a) and 9b), i.e., according to the implementation modality in which there is consumption of methane as fuel and consumption of exogenous CO2 for the production of conditioned syngas, theoperation of the apparatus provides that by feeding 16 kg / h of methane, 85 kg / h of CO2, 176 kg / h of H2O of which 48 kg / h from recycle and 576 kWh, 152 kg / h of conditioned syngas and 77 kg / h of pure oxygen (net of 64 kg / h of self-consumption) are produced.

[0135] Example 4: Apparatus for the production of e-fuels

[0136] According to the preferred alternative described in Figures 10a) and 10b), i.e., according to the implementation modality in which there is consumption of methane as fuel and consumption of exogenous CO2 for the production of e-fuels, the operation of the apparatus provides that by feeding 16 kg / h of methane, 85 kg / h of exogenous CO2, 176 kg / h of water (of which 103 kg / h from recycle) and 576 kWh, it is possible to produce 89 kg / h of methanol and 77 kg / h of oxygen with a surplus of 8 kg / h of syngas purge stream (recyclable as fuel).

[0137] BIBLIOGRAPHY

[0138] Hillestad et al., 2018, Improving carbon efficiency and profitability of the biomass to liquid process with hydrogen from renewable power, Fuel, 234, 1431-1451.

[0139] Vita et al. 2018, Methanol synthesis from biogas: A thermodynamic analysis, Renewable Energy, 118, pp. 673-684.

[0140] Quirino et al., 2020, Modeling and Simulation of an Industrial Top-Fired Methane Steam Reforming Unit, Industrial and Engineering Chemistry Research, 59(24), pp.

[0141] 11250-11264.

[0142] Quirino et al., 2022, Mapping and optimization of an industrial steam methane reformer by the design of experiments (DOE), Chemical Engineering Research and Design, 184, pp. 349-365.

[0143] Bozzano and Manenti, 2016, Efficient methanol synthesis: Perspectives, technologies and optimization strategies, Progress in Energy and Combustion Science, 2016, Volume 56, Pages 71 - 105, 2016.

Claims

CLAIMS1. An apparatus (100) for the production of hydrogen by means of electrolysis of water, comprising a central body (120) consisting of a refractory chamber and comprising: - a first zone (101) comprising or consisting of a burner, in which the combustion between a fuel and oxygen occurs, the fuel being selected from the group consisting of: hydrogen, a C1-C5 hydrocarbon or mixtures thereof, preferably hydrogen or methane;- a second zone (102), directly connected with the first zone (101) and arranged downstream of the latter, said second zone (102) being provided with devices (111) for controlling the temperature of the combusted gas exiting from said first zone and for regulating and delivering a coolant selected from water and / or CO2 to cool the combusted gases exiting from said first zone, said devices being able to regulate the flow rate of coolant to be flowed into said second zone (102) as a function of the temperature reached by the combusted gases exiting from said first zone (101); and - a third zone (103), directly connected with the second zone (102), said third zone (103) comprising or consisting of a high-temperature solid oxide electrolytic cell (SOEC),said apparatus (100) further comprising:- upstream of said central body (120) at least one supply line (104), (105) and (106) for supplying respectively and separately or in premixing the following compounds: Al) the fuel;A2) oxygen andA3) a diluent selected from water and CO2, and- directly connected with the third zone (103) of the central body:B) an outlet line (107), and (108) for each of the following compounds produced in the central body (120):Bl) hydrogen, any carbonaceous combusted gases and any residual steam;B2) oxygen and any residual steam.

2. The apparatus according to claim 1, wherein the outlet line for oxygen (108) produced in the third zone (103) of the central body (120) is connected via a recycle line (109) with the supply line (105) for oxygen entering the central body (120) and optionally with an outlet line (112) for conveying the produced oxygen externally to said central body (120).

3. The apparatus according to claim 2, wherein the outlet line for oxygen (108) is connected only with the recycle line (109).

4. The apparatus according to claim 2, wherein said outlet line for oxygen (108) and said recycle line (109) are internal to the central body (120).

5. The apparatus according to any one of claims 1-4, comprising an outlet and recycle line for hydrogen (110) connected to the supply line for the fuel (104) entering the first zone (101) of the central body (120).

6. The apparatus according to claim 5, wherein said outlet and recycle line for hydrogen (110) is internal to the central body (120).

7. A process for the production of hydrogen comprising:a) burning a fuel selected from hydrogen, a C1-C5 hydrocarbon or mixtures thereof, preferably hydrogen or methane, in the presence of oxygen and a diluent selected from water and CO2;b) optionally cooling the combusted gas and the diluent coming from step a) by delivering a flow rate of a coolant selected from water and / or CO2 as a function of the temperature at the outlet of step a);c) carrying out the electrolysis of water in a high-temperature solid oxide electrolytic cell (SOEC), on the combusted gas coming from step a) orb) according to the reaction:[R1]: H2O = H2+1 / 2O2;said process being conducted in the apparatus (100) according to any one of claims 1-6, wherein step a) is conducted in the first zone (101) of the central body (120); step b) of cooling the combusted gases is conducted in the second zone (102) of the central body (120) and step c) is conducted in the third zone (103) of the central body (120).

8. The process for the production of hydrogen according to claim 7, conducted in the apparatus according to claim 1, wherein methane is used as fuel, which is blown via the inlet (104), together with the oxygen via the inlet (105), and with the diluent via the inlet (106) into the first zone (101) of the central body (120) where step a) is conducted, where CO2 and steam are formed according to the reaction:[R3] : CH4+ 2 O2= CO2+ 2 H2O;the products obtained in the said reaction and the diluent are cooled in the second zone (102); the cooled combusted gases, obtained in step b) and coming from the second zone (102) enter the third zone (103) where step c) of electrolysis in a solid oxide cell is conducted; the humid hydrogen obtained in the third zone (103) exits the central body (120) via the outlet (107) together with the CO2, produced in step a) while the oxygen exits the central body (120) via the outlet (108) dedicated to it.

9. The process according to claim 8, conducted in the apparatus according to claim 1, wherein in the second zone (102) of the central body (120) the CO2 and the steam, which have a temperature below 1500°C, are cooled to a temperature below 1000°C, preferably below 900°C and more preferably ranging between 700 and 900°C.

10. The process for the production of hydrogen according to claim 7, conducted in the apparatus according to claim 1, wherein when the fuel is hydrogen it is blown via the inlet line (104) together with the oxygen via the inlet (105) and with the diluent via theinlet (106) into the first zone (101) of the central body (120) where step a) is conducted and where steam is formed according to the reaction:[R2] H2+ 0.5 O2= H2Owhich exits from the first zone (101) of the central body (120) at a temperature lower than or equal to 1500°C, preferably lower than 1000°C and more preferably at a temperature ranging between 800°C and 1000°C and is cooled in the second zone (102) by means of the water delivery devices (111) at the preferred temperature ranging between 700 and 900°C before entering the third zone (103), in which the electrolysis reaction is conducted and via the outlet (107) only humid hydrogen exits, while the oxygen exits the central body (120) via the outlet (108).

11. The process according to any one of claims 7-10, conducted in the apparatus according to claim 3, wherein the oxygen produced in step c) and in the third zone (103) of the central body (120) exits via the outlet (108) connected only to the recycle line (109) and is fed via the inlet (105) into the first zone (101) of the central body (120).

12. The process according to any one of claims 7-10, conducted in the apparatus according to claim 4, wherein the oxygen produced in step c) exits the central body (120) via the outlet (108) and is:• partly recycled via the recycle line (109) and introduced via the inlet (105) into the central body in the first reaction zone (101) and• partly exits the central body (120) via the line (112).

13. The process according to any one of claims 7-10, conducted in the apparatus according to claim 5 or 6, wherein part of the hydrogen produced in step c) in the third zone (103) of the central body (120) is recycled via the line (110) and enters the first zone (101) of the central body (120).

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