Process for salvaging flue gas heat and system therefor

Abstract

The present disclosure relates to a method of using flue gas heat resulting from a combustion reaction, comprising: a) providing a fuel and an oxidant; b) preheating the fuel and the oxidant to produce a preheated fuel and a preheated oxidant; c) feeding the preheated fuel and preheated oxidant to a combustion chamber; d) heating raw materials via the combustion reaction of the preheated fuel with the preheated oxidant in the combustion chamber and generating flue gas; e) transferring at least part of the heat of the flue gas exiting the combustion chamber to an intermediate fluid, thereby producing a heated intermediate fluid; f) heating a Solid Oxide Electrolyzer Cells (SOEC) unit to a SOEC operating temperature, g) exchanging heat using at least part of the heat of the heated intermediate fluid, h) providing a steam stream at a steam stream temperature and an oxygen-containing carrier gas at an oxygen-containing carrier gas temperature, and feeding the steam stream and the oxygen-containing carrier gas to the SOEC unit to produce an oxygen-containing stream and a hydrogen-containing stream; wherein exchanging heat comprises 1. preheating the fuel to produce the preheated fuel to be fed to the combustion chamber and / or 2. preheating the oxidant to produce the preheated oxidant to be fed to the combustion chamber. The present disclosure also relates to a system of using flue gas heat from a combustion reaction.

Description

Process for salvaging flue gas heat and system thereforTECHNICAL FIELD

[0001] The present disclosure relates to methods and systems of using flue gas heat resulting from a combustion reaction. In particular, the present disclosure relates to methods and systems using a Solid Oxide Electrolyzer Cells (SOEC) unit and an intermediate fluid heated by flue gas heat resulting from a combustion reaction.BACKGROUND ART

[0002] Traditionally, natural gas as fuel and air as an oxidant (NG / Air) have been used in processes relying on the delivery of large amounts of heat energy into a furnace by combustion of the fuel. The combustion generates a hot flue gas mainly comprising CO2, H2O and traces of suspended particulate matter (SPM, e.g., silicon oxides).

[0003] Nowadays, the global glass industry emits about 86 Mt CCb / year, and about 80% of those CO2 emissions originate from the flat glass and container-glass production.

[0004] High-quality flat glasses for buildings and the automotive industry are manufactured by float glass manufacturing processes.

[0005] In float glass manufacturing processes, a continuous strip of molten glass is produced by heating raw materials from about 25 °C to about 1500 °C via NG / Air combustion before being poured from a furnace onto a large shallow bath of molten metal (about 600 °C), typically containing a tin bath. Glass floats and cools down on the bath and spreads out to form a flat surface. A typical mixture of 3% H2 balance N2 is used as a protective atmosphere in the bath in order to avoid tin oxidation.

[0006] Flat glasses have to fulfil very strict quality requirements, such as less than two bubbles / glass and less than one stone / glass. Due to these constraints, the meltingprocess in a float glass manufacturing process is quite different from usual glass furnaces.

[0007] NG / Air combustion provides a reliable heat distribution inside melting chambers. However, it also releases a high amount of CO2 emissions from the fuel (NG) and has a low combustion efficiency.

[0008] The large CO2 emissions in float glass manufacturing processes are due to the massive use of NG / Air for the combustion and to the inherent high carbon content of the raw materials, which typically include limestone, soda ash, dolomite and glass cullets.

[0009] Recently, natural gas oxycombustion (NG / O2) has been targeted to mitigate the CO2 emissions and also increase the combustion efficiency.

[0010] Even though it is a common practice to recover excess heat in the flue gas, for example, by using it to heat air for combustion, due to technical constraints, such a recovery is generally not realized in the case of using oxygen instead of air for the combustion.

[0011] As a route to eliminate the CO2 emission from fuel combustion, H2 / O2 combustion has been gathering recent interest, but its use in industrial processes, such as in float glass manufacturing processes, has not been extensively evaluated yet.

[0012] There is thus a need in the art for improved combustion efficiency using new cleaner gases in order to reduce the CO2 footprint in processes involving combustion reactions, particularly in, but not limited to, the glass industry, for example the float glass industry, or the cement industry.SUMMARY OF INVENTION

[0013] The inventors have found a way to reuse the flue gas heat from a combustion chamber into a high temperature SOEC unit to produce low-carbon H2 and O2.Additionally, the inventors have found that further reuse of the flue gas heat for preheating the fuel and / or oxidant via an intermediate fluid in addition to the thermal integration of the SOEC unit increases the efficiency of the process.

[0014] Thus, the present invention relates to a method of using flue gas heat resulting from a combustion reaction according to claim 1 and a system of using flue gas heat from a combustion reaction according to claim 15. Advantageous embodiments may include features of dependent claims.Definitions

[0015] The singular forms “a”, “an” and “the” include plural referents, unless the context clearly dictates otherwise.

[0016] “Comprising” in this description and in the claims is meant to be an open transitional term, which means that subsequently identified claim elements are a nonexclusive listing, i.e. , anything else may be additionally included and remain within the scope of “comprising.” "Comprising" as used herein may be replaced by the more limited transitional terms "consisting essentially of" and "consisting of unless otherwise indicated herein. The expression "consisting essentially of" is to be interpreted as allowing the presence of other elements in addition to the mandatory elements, in the form of impurities.

[0017] “Providing” herein is defined to mean furnishing, supplying, making available, or preparing something. The step may be performed by any actor in the absence of express language to the contrary.

[0018] “Optional” or “optionally” means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.

[0019] Ranges may be expressed herein as from about one particular value, and / or to about another particular value. When such a range is expressed, it is to be understood thatanother embodiment is from the one particular value and / or to the other particular value, along with all combinations within said range.

[0020] As used herein, the term “substantially free” refers to a gas or mixture that does not contain a particular compound or to which a particular compound has not been added.

[0021] As used herein, the term “about” is used to mean that a variable such as a temperature or a concentration may be within a range of 10% below or above the indicated value, preferably 5% below or above the indicated value, more preferably 1% below or above the indicated value, and even more preferably the indicated value.

[0022] It should be noted that in specifying any range of temperature, any upper temperature can be associated with any lower temperature.

[0023] The term “and / or” includes the meanings “and”, “or” and also all the other possible combinations of the elements connected to this term.

[0024] As used herein, the term “air” is used to mean dry air comprising oxygen in a range of about 20.95 vol%.

[0025] The SOEC unit operates at temperatures that allow high temperature electrolysis reactions to take place. The net cell reaction produces hydrogen and oxygen. The reactions at the cathode and the anode are shown below for one mole of water: Cathode: H2O + 2 e- — ► H2 + O2 ■ Anode: 02' O2 + 2 e-Net reaction: H2O — ► H2 + 0.5 O2

[0026] As used herein, the term “hydrogen-containing stream” is used to mean a stream comprising hydrogen. The hydrogen-containing stream may also comprise steam.

[0027] As used herein, the term “oxygen-containing stream” is used to mean a stream comprising oxygen enriched air, i.e., comprising an oxygen content higher than air. The “oxygen-containing stream” may be substantially free of water or steam.

[0028] As used herein, the “hydrogen gas” is used to mean a gas comprising hydrogen as a major ingredient, i.e., comprising at least about 80 vol%, preferably at least about 90 vol%, more preferably at least about 94 vol%, even more preferably at least about 96 vol%, still even more preferably at least about 99 vol%, and most preferably at least about 99.8 vol% of hydrogen.

[0029] As used herein, the “oxygen gas” is used to mean a gas comprising oxygen as a major ingredient, i.e., comprising at least about 80 vol%, preferably at least about 90 vol%, more preferably at least about 94 vol%, even more preferably at least about 96 vol%, still even more preferably at least about 99 vol%, and most preferably at least about 99.8 vol% of oxygen.

[0030] As used herein, the term “oxidant” is used to mean a gas containing oxygen. The gas containing oxygen may be, but is not limited to, pure oxygen (as defined in the industry), air, oxygen gas as defined above, oxygen enriched air comprising an oxygen content higher than air, an oxygen-containing stream or combinations thereof.

[0031] As used herein, the term “natural gas” is used to mean a mixture of gaseous hydrocarbons, if not specified otherwise, preferably comprising methane (CH4), optionally with smaller amounts of various other alkanes.

[0032] As used herein, the term “fuel” is used to mean a substance that is reacted with an oxidant so that it releases thermal energy. The fuel may be, but is not limited to, natural gas, ammonia (NH3) or a gas containing hydrogen such as hydrogen gas as defined above, a hydrogen-containing stream as defined above, or combinations thereof.

[0033] As used herein, the term “water source” is used to mean a water reservoir at liquid phase.

[0034] As used herein, the term “steam source” is used to mean a saturated or superheated gaseous steam reservoir at a temperature below the steam stream temperature (SOEC operation temperature).

[0035] As used herein, the term “steam stream” is used to mean a superheated gaseous steam at a steam stream temperature, which is a temperature superior to the temperature at the steam source.

[0036] As used herein, the term “steam stream temperature” is used to mean the SOEC operating temperature.

[0037] Herein, the term “HeatOx™” refers to a system in which an intermediate fluid is first heated in a recuperator through heat exchange with a hot flue gas, and subsequently, the oxidant and / or the fuel is preheated with the heated intermediate fluid in a separate shell and tube heat exchanger, for example as in WO2016 / 102621 A1.Description of the invention

[0038] As such, in a first aspect, the present invention relates to a method of using flue gas heat resulting from a combustion reaction, comprising: a) providing a fuel and an oxidant; b) preheating the fuel and the oxidant to produce a preheated fuel and a preheated oxidant; c) feeding the preheated fuel and preheated oxidant to a combustion chamber; d) heating raw materials via the combustion reaction of the preheated fuel with the preheated oxidant in the combustion chamber and generating flue gas; e) transferring at least part of the heat of the flue gas exiting the combustion chamber to an intermediate fluid, thereby producing a heated intermediate fluid;f) heating a Solid Oxide Electrolyzer Cells (SOEC) unit to a SOEC operating temperature; g) exchanging heat using at least part of the heat of the heated intermediate fluid; h) providing a steam stream at a steam stream temperature and an oxygencontaining carrier gas at an oxygen-containing carrier gas temperature, and feeding the steam stream and the oxygen-containing carrier gas to the SOEC unit to produce an oxygen-containing stream and a hydrogen-containing stream; wherein exchanging heat comprises:1. preheating the fuel to produce the preheated fuel to be fed to the combustion chamber and / or2. preheating the oxidant to produce the preheated oxidant to be fed to the combustion chamber.

[0039] In typical commercial furnaces, the flue gas is typically and preferably hot, having a temperature ranging from about 1000° to about 1800°C. In some processes such as found in the glass industry, the flue gas frequently carries particulates, or toxic species such as SO2, NOx, CO, and unburned hydrocarbons. The flue gas may also comprise corrosive components such as NaOH, sulfates, borates and the like in volatilized form.

[0040] In some embodiments, the SOEC operating temperature and the steam stream temperature may be in the range of about 600°C to about 900°C, preferably about 600°C to about 850°C, more preferably about 600°C to about 800°C, and even more preferably about 600°C to about 750°C.

[0041] The oxygen-containing carrier gas temperature, the temperature of the oxygencontaining stream and the hydrogen-containing stream are the same as the SOEC operating temperature and the steam stream temperature.

[0042] In some embodiments, the oxygen-containing carrier gas may be pure oxygen (as defined in the industry), air or oxygen enriched air comprising an oxygen content higher than air. For example, the oxygen enriched air may comprise higher than about 20.95 vol%, at least about 22 vol%, at least about 23 vol%, at least about 24 vol%, at least about 25 vol%, at least about 26 vol%, at least about 27 vol%, a leastabout 28 vol% of oxygen. The oxygen-containing carrier gas is preferably air. The oxygen-containing carrier gas may be substantially free of water or steam.

[0043] In some embodiments, typically, the hydrogen-containing stream may comprise steam in a range of about 10 vol% to about 30 vol%. More typically, the hydrogencontaining steam may comprise about 15 vol% of steam. However, the content of steam may vary greatly depending on the balance of stack and operating conditions.

[0044] In some embodiments, the oxygen-containing stream may comprise higher than about 20.95 vol%, preferably at least about 23 vol%, more preferably at least about 26 vol%, even more preferably at least about 28 vol%, and still even more preferably at least about 30 vol% of oxygen.

[0045] In some embodiments, the intermediate fluid may be preferably clean, non-toxic, non-combustible, and substantially non-corrosive. Further, the intermediate fluid must be capable of being heated to about 600°C to about 1600°C in a heat transfer means by the flue gases. Preferred fluids include gases such as air, nitrogen, carbon dioxide, water vapor, and the like. Other preferred fluids may include liquids, such as water, glycols, and the like, including mixtures of same. Air is a particularly preferred intermediate fluid for use in the present invention.

[0046] In some embodiments, the temperature of the heated intermediate fluid after heat transfer with the at least part of the heat of the flue gas exiting the combustion chamber may be at least about 20°C, preferably at least about 25°C, more preferably at least about 50°C, and even more preferably at least about 100°C higher than the SOEC operating temperature.

[0047] In some embodiments, the oxidant may be preheated to a temperature in the range of about 200°C to about 800°C, preferably about 550°C. The fuel may be preheated to a temperature in the range of about 200°C to about 500°C, preferably about 450°C.

[0048] In some embodiments, heating the SOEC unit to the SOEC operating temperature may be performed partially or wholly by using at least part of the heat of the heatedintermediate fluid. In some other embodiments, heating the SOEC unit to the SOEC operating temperature may be performed purely electrically.

[0049] Heating the SOEC unit to the SOEC operating temperature partially by using at least part of the heat of the heated intermediate fluid means that at least part of the heat of the heated intermediate fluid may provide partially the power necessary for heating the SOEC unit to the SOEC operating temperature. In that case, the remaining power may be provided by electricity. In that case, the power provided by the external medium may represent between higher than 0% to less than 100%, preferably between more than 0% to about 30%, more preferably between more than 0% to about 20%, and even more preferably between more than 0% to about 10% of the total power necessary to heat the SOEC to the SOEC operating temperature.

[0050] Heating the SOEC unit to the SOEC operating temperature wholly by using at least part of the heat of the heated intermediate fluid means that at least part of the heat of the heated intermediate fluid may provide for 100% of the power necessary for heating the SOEC unit to the SOEC operating temperature.

[0051] In some embodiments, exchanging heat may comprise preheating the fuel to produce the preheated fuel to be fed to the combustion chamber and preheating the oxidant to produce the preheated oxidant to be fed to the combustion chamber.

[0052] In some embodiments, the method may further comprise providing a cool oxygencontaining carrier gas at a temperature lower than the oxygen-containing carrier gas temperature, and exchanging heat may further comprise heating the cool oxygencontaining carrier to produce the oxygen-containing carrier gas to be fed to the SOEC unit at the oxygen-containing carrier gas temperature.

[0053] In some embodiments, the temperature of the cool oxygen-containing carrier gas may be in the range from room temperature to about 60°C, preferably in the range from room temperature to about 50°C.

[0054] In some embodiments, the method may further comprise providing a water source or a steam source at a temperature lower than the steam stream temperature, andexchanging heat may further comprise heating the water source or the steam source to produce the steam stream to be fed to the SOEC unit at the steam stream temperature.

[0055] As mentioned above, the water source is water reservoir at liquid phase. In some embodiments, the temperature of the water source may be in the range of room temperature to about 150°C, preferably room temperature to about 100°C, and more preferably room temperature to about 80°C. The steam source is a saturated or superheated gaseous steam reservoir at temperature below the steam stream temperature. The temperature of the steam source depends on the pressure of the steam source and may be in the range of about 100°C to about 550°C, preferably about 120°C to about 450°C, more preferably about 130°C to about 300°C, and even more preferably about 140°C to about 160°C.

[0056] In some embodiments, using at least part of the heat of the heated intermediate fluid may comprise splitting the heated intermediate fluid into a plurality of streams for exchanging heat and, optionally, for heating the SOEC unit. In a preferred embodiment, exchanging heat may comprise preheating the oxidant, preheating the fuel, heating the oxygen-containing carrier gas, and heating the water source or the steam source. In one exemplary embodiment of the preferred embodiment, the plurality of streams may be used to preheat the fuel, to preheat the oxidant, to preheat the oxygen-containing carrier gas, to heat the SOEC unit, and to heat the water source or the steam source.

[0057] In some other embodiments, using at least part of the heat of the heated intermediate fluid may comprise sequentially exchanging heat and, optionally, heating the SOEC unit. The sequence may be adjusted to minimize the number and / or size of heat exchangers and extract maximum heat from the heated intermediate fluid without violating thermodynamic temperature cross over. In a preferred embodiment, exchanging heat may comprise preheating the oxidant, preheating the fuel, heating the oxygen-containing carrier gas, and heating the water source or the steam source. In one exemplary embodiment of the preferred embodiment, at least part of the heat of the heated intermediate fluid may be used to sequentially heat the oxygen-containing carrier gas, the SOEC unit, to heat the water source or the steam source, to preheat the oxidant, and to preheat the fuel, in that order.

[0058] In still some other embodiments, using at least part of the heat of the heated intermediate fluid may comprise splitting the heated intermediate fluid into two or more streams to sequentially exchange heat (and, optionally, heat the SOEC unit) with one stream, and further exchange heat with the remaining stream(s). The sequence of exchanging heat with one stream and, optionally, heating the SOEC unit may be adjusted to minimize the number and / or size of heat exchangers and extract maximum heat from the heated intermediate fluid without violating thermodynamic temperature cross over. In one embodiment, exchanging heat and, optionally, heating the SOEC unit with one stream may comprise heating the oxygen-containing carrier gas and / or heating the water source or the steam source, and, optionally, heating the SOEC in any sequential order. Further exchanging heat with the remaining stream(s) may comprise preheating the oxidant and / or preheating the fuel. When exchanging heat comprises preheating the fuel and preheating the oxidant, according to one embodiment, the remaining stream(s) may comprise one stream to be used to preheat the oxidant and preheat the fuel, in that order. According to another embodiment, the remaining stream(s) may comprise two streams to be used to preheat the fuel and preheat the oxidant, separately. In a preferred embodiment, exchanging heat may comprise preheating the oxidant, preheating the fuel, heating the oxygen-containing carrier gas, and heating the water source or the steam source. In one exemplary embodiment of the preferred embodiment, using at least part of the heat of the heated intermediate fluid comprises splitting the heated intermediate fluid into two streams to sequentially heat the oxygen-containing gas carrier, the SOEC unit, and the water source or the steam source with a first stream in that order; and to sequentially preheat the oxidant, and preheat the fuel, with a second stream, in that order. In another exemplary embodiment of the preferred embodiment, using at least part of the heat of the heated intermediate fluid comprises splitting the heated intermediate fluid into three streams. A first stream is used to sequentially heat the oxygen-containing gas carrier, the SOEC unit, and the water source or the steam source in that order. A second stream is used to preheat the fuel, and a third stream is used to preheat the oxidant.

[0059] In some embodiments, the method may further comprise heating or preheating the water source or the steam source by using at least part of the heat of the hydrogencontaining stream, thereby cooling the hydrogen-containing stream and producing a cooled hydrogen-containing stream.

[0060] In some embodiments, heating the water source or steam source by using at least part of the heat of the hydrogen-containing stream produces a saturated gaseous steam or superheated gaseous steam at a temperature lower than the steam stream temperature. The temperature of the saturated gaseous steam or superheated gaseous steam may then be in the range of about 20°C to about 150°C below the steam stream temperature. A preferred temperature may be in any one of the following ranges: about 20°C to about 140°C, about 20°C to about 120°C, about 20°C to about 100°C, about 20°C to about 80°C, about 20°C to about 60°C, about 20°C to about 40°C, about 20°C to about 30°C below the steam stream temperature. Exchanging heat may then further comprise heating the saturated gaseous steam or superheated gaseous steam thus produced to produce the steam stream to be fed to the SOEC unit at the steam stream temperature.

[0061] The temperature of the cooled hydrogen-containing stream may be in the range of about 50°C to about 180°C, more preferably about 50°C to about 130°C, and even more preferably about 50°C to about 120°C.

[0062] In some embodiments, the method may further comprise recovering water or steam from at least a part of the cooled hydrogen-containing stream, thereby producing recovered water or steam.

[0063] In some embodiments, the method may further comprise using at least part of the recovered water or steam as at least part of the water source or steam source.

[0064] In some embodiments, the method may further comprise directly using at least part of the cooled hydrogen-containing stream as at least part of the fuel.

[0065] In some embodiments, the method may further comprise recovering hydrogen gas from at least a part of the cooled hydrogen-containing stream, thereby producing a recovered hydrogen gas.

[0066] In some embodiments, the method may further comprise using at least part of the recovered hydrogen gas as at least part of the fuel.

[0067] In some embodiments, the method may further comprise feeding at least part of the hydrogen-containing stream to the SOEC unit along with the steam stream at the steam stream temperature.

[0068] In some embodiments, the method may further comprise preheating at least part of the recovered hydrogen gas by using at least part of the heat of the hydrogen-containing stream, thereby producing preheated recovered hydrogen gas. In that case, exchanging heat may further comprise heating the preheated recovered hydrogen gas to the steam stream temperature, thereby producing heated recovered hydrogen gas. The method may then further comprise feeding the heated recovered hydrogen gas to the SOEC unit along with the steam stream.

[0069] In some embodiments, the method may further comprise heating or preheating the water source or steam source or preheating the cool oxygen-containing carrier gas by using at least part of the heat of the oxygen-containing stream, thereby cooling the oxygen-containing steam and producing a cooled oxygen-containing stream.

[0070] In the case where the method comprises heating the water source or steam source by using at least part of the heat of the oxygen-containing stream, thereby cooling the oxygen-containing steam and producing a cooled oxygen-containing stream, heating the water source or steam source by using at least part of the heat of the oxygencontaining stream may produce a saturated gaseous steam or superheated gaseous steam at a temperature lower than the steam stream temperature. The temperature of the saturated gaseous steam or superheated gaseous steam may be in the range of about 20°C to about 150°C below the oxygen-containing stream temperature. A preferred temperature may be in any one of the following ranges: about 20°C toabout 140°C, about 20°C to about 120°C, about 20°C to about 100°C, about 20°C to about 80°C, about 20°C to about 60°C, about 20°C to about 40°C below the oxygencontaining stream temperature. Exchanging heat may then further comprise heating the saturated gaseous steam or superheated gaseous steam thus produced to produce the steam stream to be fed to the SOEC unit at the steam stream temperature.

[0071] In the case where the method further comprises heating the water source or steam source by using at least part of the heat of the oxygen-containing stream, thereby cooling the oxygen-containing steam and producing a cooled oxygen-containing stream, heating the water source or steam source may produce a saturated gaseous steam or a first superheated gaseous steam at a temperature lower than the steam stream temperature. The temperature of the saturated gaseous steam or first superheated gaseous steam may be in the range of about 20°C to about 100°C below the oxygen-containing stream temperature. A preferred temperature may be in any one of the following ranges: about 20°C to about 90°C, about 20°C to about 80°C, about 20°C to about 70°C, about 20°C to about 60°C, about 20°C to about 50°C, about 20°C to about 40°C below the oxygen-containing stream temperature. The saturated gaseous steam or first superheated gaseous steam may then be heated by using at least part of the heat of the hydrogen-containing stream, thereby cooling the hydrogen-containing stream and producing a cooled hydrogen-containing stream. Heating the saturated gaseous steam or first superheated gaseous steam by using at least part of the heat of the hydrogen-containing stream may produce a superheated gaseous steam or a second superheated gaseous steam at a temperature lower than the steam stream temperature, but higher than the saturated gaseous steam or superheated gaseous temperature of the previous step. The temperature of the superheated gaseous steam or second superheated gaseous steam may be in the range of about 20°C to about 150°C below the hydrogencontaining stream temperature, provided that it is higher than the temperature of the saturated gaseous steam or first superheated gaseous steam. A preferred temperature may be in any one of the following ranges: about 20°C to about 140°C, about 20°C to about 120°C, about 20°C to about 100°C, about 20°C to about 80°C, about 20°C to about 60°C, about 20°C to about 40°C below the hydrogen-containing stream temperature. Exchanging heat may then further comprise heating the secondsuperheated gaseous steam at a temperature lower than the steam stream temperature to produce the steam stream to be fed to the SOEC unit at the steam stream temperature.

[0072] In the case where the method further comprises preheating the cool oxygencontaining carrier gas by using at least part of the heat of the oxygen-containing stream, thereby cooling the oxygen-containing stream and producing a cooled oxygen-containing stream, the sequence of steps may be as follows. The cool oxygen-containing carrier gas is preheated by using at least part of the heat of the oxygen-containing stream, thereby producing a preheated oxygen-containing carrier gas. The temperature of the cool oxygen-containing carrier gas is as defined above. The temperature of the preheated oxygen-containing carrier gas may be in the range of about 20°C to about 170°C below the oxygen-containing carrier gas temperature. A preferred temperature may be in any one of the following ranges: about 20°C to about 160°C, about 20°C to about 140°C, about 20°C to about 120°C, about 20°C to about 100°C, about 20°C to about 80°C, about 20°C to about 60°C below the oxygen-containing stream temperature. Exchanging heat may then further comprise heating the preheated oxygen-containing carrier gas to produce the oxygencontaining carrier gas to be fed to the SOEC unit at the oxygen-containing carrier gas temperature.

[0073] The temperature of the cooled oxygen-containing stream may be in the range of about room temperature to about 200°C, preferably room temperature to about 180°C, more preferably room temperature to about 100°C, and even more preferably room temperature to about 60°C.

[0074] In some embodiments, the method may further comprise recovering oxygen gas from at least part of the cooled oxygen-containing stream, thereby producing recovered oxygen gas.

[0075] In some embodiments, the method may further comprise using at least part of the recovered oxygen gas as at least part of the oxidant.

[0076] In some embodiments, the method may further comprise directly using at least part of the cooled oxygen-containing stream as at least part of the oxidant.

[0077] In some embodiments, exchanging heat may comprise preheating the fuel, preheating the oxidant, preheating the oxygen-containing carrier gas, heating the water source or steam source, and heating the preheated recovered hydrogen gas to the steam stream temperature. In one further embodiment, using at least part of the heat of the heated intermediate fluid may comprise splitting the heated intermediate fluid into a plurality of streams for exchanging heat, i.e. , preheating the fuel, preheating the oxidant, preheating the oxygen-containing carrier gas, heating the water source or the steam source, and heating the preheated recovered hydrogen gas, and, optionally, heating the SOEC unit. In another further embodiment, using at least part of the heat of the heated intermediate fluid may comprise sequentially exchanging heat and, optionally, heating the SOEC unit. The sequence may be adjusted to minimize the number and / or size of heat exchangers and extract maximum heat from the heated intermediate fluid without violating thermodynamic temperature cross over. In one exemplary embodiment, at least part of the heat of the heated intermediate fluid is used to sequentially heat the oxygen-containing carrier gas, heat the water source or the steam source, heat the SOEC unit, heat the preheated recovered hydrogen gas, to preheat the oxidant, and to preheat the fuel, in that order. In still another further embodiment, using at least part of the heat of the heated intermediate fluid may comprise splitting the heated intermediate fluid into one or more streams to sequentially exchange heat (and, optionally, heat the SOEC unit) with one stream, and further exchange heat with the remaining stream(s). The sequence of exchanging heat, and optionally, heating the SOEC unit with the one stream may be adjusted to minimize the number and / or size of heat exchangers and extract maximum heat from the heated intermediate fluid without violating thermodynamic temperature cross over. The sequence of exchanging heat and, optionally, heating the SOEC unit with one stream may thus comprise heating the oxygen-containing carrier gas, heating the water source or the steam source, heating the preheated recovered hydrogen gas, and, optionally, heating the SOEC in any sequential order. According to one embodiment, the remaining stream(s) may comprise one stream to be used to preheat the oxidant and preheat the fuel, in thatorder. According to another embodiment, the remaining stream(s) may comprise two streams to be used to preheat the fuel and preheat the oxidant, separately. In one exemplary embodiment, the heated intermediate fluid is split into two streams to sequentially heat the oxygen-containing gas carrier, the SOEC unit, the preheated recovered hydrogen gas, and the water source or the steam source with a first stream, in that order; and to sequentially preheat the oxidant, and preheat the fuel, with a second stream, in that order. In another exemplary embodiment, the heated intermediate fluid is split into three streams. A first stream is used to sequentially heat the oxygen-containing gas carrier, the SOEC unit, the preheated recovered hydrogen gas, and the water source or the steam source, in that order. A second stream is used to preheat the fuel, and a third stream is used to preheat the oxidant.

[0078] In some embodiments, the raw materials may be glass raw materials or cement raw materials. The glass raw materials may include recycled glass, commonly referred to as cullet, and other minerals and chemicals in a pulverized form referred to as batch materials that have a relatively high water content. Preferably, the glass raw materials include limestone, soda ash, dolomite and glass cullets. The cement raw materials may typically include limestone, shells, and chalk or marl combined with shale, clay, slate, blast furnace slag, silica sand, and / or iron ore.

[0079] In some embodiments, the method may further comprise using at least part of the recovered hydrogen gas in a glass manufacturing process. Preferably, using at least part of the recovered hydrogen gas may comprise feeding the atmosphere of a tin bath in a float glass manufacturing process with the at least part of the recovered hydrogen gas.

[0080] In some embodiments, exchanging heat may provide the whole energy to heat the different sources, gases, or streams to their predetermined temperatures. In some other embodiments, exchanging heat may provide only the partial energy needed to heat the different sources, gases, or streams to their predetermined temperature, that is, higher than 0% to less than 100%, preferably between more than 0% to about 30%, more preferably between more than 0% to about 20%, and even more preferably between more than 0% to about 10% of the total power needed for eachsource, gas, or stream. In that case, the remaining energy may be provided by electrical heating.

[0081] Another aspect of the present invention relates to a system of using flue gas heat from a combustion reaction, comprising:- a Solid Oxide Electrolyzer Cells (SOEC) unit operable to a SOEC operating temperature to produce an oxygen-containing stream and a hydrogen-containing stream, wherein the SOEC unit is configured to receive a steam stream at a steam stream temperature and an oxygen-containing carrier gas at oxygen-containing carrier gas temperature,- a primary heat exchanger for transferring at least part of the heat of flue gas to an intermediate fluid to produce a heated intermediate fluid, the flue gas being produced by the combustion reaction for heating raw materials and exiting a combustion chamber;- one or more secondary heat exchangers comprising a first heat exchanger for preheating a fuel to produce the preheated fuel to be fed to the combustion chamber; and / or a second heat exchanger for preheating an oxidant to produce the preheated oxidant to be fed to the combustion chamber; and / or a third heat exchanger for heating a cool oxygen-containing carrier gas at a temperature lower than the oxygen-containing carrier gas temperature to produce the oxygen-containing carrier gas to be fed to the SOEC unit; and / or a fourth heat exchanger for heating a water source or a steam source to produce the steam stream to be fed to the SOEC unit;-optionally, a tertiary heat exchanger for heating or preheating the water source or the steam source using at least part of the heat of the hydrogen-containing stream, and / or a quaternary heat exchanger for heating or preheating the water source or the steam source using at least part of the heat of the oxygen-containing stream and / or for preheating the cool oxygen-containing carrier gas, wherein the system is configured to use at least part of the heat of the heated intermediate fluid for exchanging heat in the one or more secondary heat exchangers.

[0082] The primary heat exchanger must be able to withstand temperatures of the flue gas. Preferably, refractory alloys, such as Inconel 600, Hasteloy, and the like, or ceramic materials are exemplary materials that may be used for the primary heat exchanger. Other suitable materials for the primary heat transfer means may include composites of metals and ceramic materials such as ceramic coated metals.

[0083] The first heat exchanger, the second heat exchanger, the third heat exchanger and the fourth heat exchanger may comprise heat exchangers selected from the group consisting of ceramic heat exchangers, metallic heat exchangers, regenerative means alternatively heated by the flow of the heated intermediate fluid and cooled by the flow of the oxidant, fuel, cool oxygen-containing carrier gas, or water source or a steam source that is heated thereby, and combinations thereof.

[0084] The water source, the stream source, the steam stream, the cool oxygen-containing carrier gas, the oxygen-containing carrier gas, the oxygen-containing stream, the hydrogen-containing stream, the flue gas, the intermediate fluid, the heated intermediate fluid, the oxidant, and the fuel, as well as their respective temperatures and the SOEC operating temperature are as defined above.

[0085] In some embodiments, the system may further be configured to use at least part of the heat of the heated intermediate fluid for partially or wholly heating the SOEC unit to the SOEC operating temperature. In some other embodiments, the system may further be configured to heat the SOEC unit purely electrically.

[0086] Partially or wholly heating the SOEC unit to the SOEC operating temperature using at least part of the heat of the heated intermediate fluid is as defined above.

[0087] In some embodiments, the primary heat exchanger may heat the intermediate fluid to produce the heated intermediate fluid at a temperature of at least about 20°C, preferably at least about 25°C, more preferably at least about 50°C, and even more preferably at least about 100°C higher than the SOEC operating temperature.

[0088] In some embodiments, the first heat exchanger may preheat the fuel to a temperature in the range of about 200°C to about 500°C, preferably about 450°C, to produce the preheated fuel.

[0089] In some embodiments, the second heat exchanger may preheat the oxidant to a temperature in the range of about 200°C to about 800°C, preferably about 550°C, to produce the preheated oxidant.

[0090] In some embodiments, the third heat exchanger may heat the cool oxygen-containing carrier gas to produce the oxygen-containing carrier gas at the oxygen-containing carrier gas temperature.

[0091] In some embodiments, the fourth heat exchanger may heat the water source or the steam source to produce the steam stream at the steam stream temperature.

[0092] In a preferred embodiment, the one or more secondary heat exchangers comprise the first heat exchanger and the second heat exchanger.

[0093] In a more preferred embodiment, the one or more secondary heat exchangers comprise the first heat exchanger, the second heat exchanger, and the third heat exchanger.

[0094] In an even more preferred embodiment, the one or more secondary heat exchangers comprise the first heat exchanger, the second heat exchanger, the third heat exchanger, and the fourth heat exchanger.

[0095] In some embodiments, the heated intermediate fluid is split into a plurality of streams to feed the one or more secondary heat exchangers and, optionally, heat the SOEC unit. In a preferred embodiment, the one or more secondary heat exchangers may comprise the first heat exchanger, the second heat exchanger, the third heat exchanger, and the fourth heat exchanger. In an exemplary embodiment of the preferred embodiment, the heated intermediate fluid is split to preheat the fuel via the first heat exchanger, to preheat the oxidant via the second heat exchanger, to heatthe oxygen-containing carrier gas via the third heat exchanger, the water source or the steam source via the fourth heat exchanger, and to heat the SOEC unit.

[0096] In some other embodiments, the heated intermediate fluid is used to sequentially feed the one or more secondary heat exchangers and, optionally, to heat the SOEC unit. The sequence of feeding the one or more secondary heat exchangers and, optionally, heating the SOEC unit may be adjusted to minimize the number and / or size of heat exchangers and extract maximum heat from the heated intermediate fluid without violating thermodynamic temperature cross over. In a preferred embodiment, the one or more secondary heat exchangers may comprise the first heat exchanger, the second heat exchanger, the third heat exchanger, and the fourth heat exchanger. In one exemplary embodiment of the preferred embodiment, the heated intermediate fluid is used to feed the third heat exchanger, to heat the SOEC unit, to feed the fourth heat exchanger, the second heat exchanger and the first heat exchanger, in that order.

[0097] In still some other embodiments, the heated intermediate fluid is split into two or more streams to (sequentially) feed at least one of the one or more heat exchangers, and, optionally, heat the SOEC unit with one stream, and feed the other one(s) of the one or more heat exchangers with the remaining stream(s). The sequence of feeding the at least one of the one or more secondary heat exchangers and, optionally, heating the SOEC unit with one stream may be adjusted to minimize the number and / or size of heat exchangers and extract maximum heat from the heated intermediate fluid without violating thermodynamic temperature cross over. In one embodiment, feeding at least one of the one or more heat exchangers and, optionally, heating the SOEC unit with one stream may comprise feeding the third heat exchanger and / or feeding the fourth heat exchanger, and, optionally heating the SOEC unit, in any sequential order, while feeding the other one(s) of the one or more heat exchangers may comprise feeding the first heat exchanger and / or feeding the second heat exchanger. When the one or more secondary heat exchangers comprise the first heat exchanger and the second heat exchanger, according to one embodiment, the remaining stream(s) may comprise one stream to be used to feed the second heat exchanger and to feed the first heat exchanger, in that order. According to another embodiment, the remaining stream(s) may comprise twostreams to be used to feed the first heat exchanger and to feed the second heat exchanger, separately. In a preferred embodiment, the one or more secondary heat exchangers may comprise the first heat exchanger, the second heat exchanger, the third heat exchanger, and the fourth heat exchanger. In an exemplary embodiment of the preferred embodiment, the heated intermediate fluid is split into two streams to sequentially feed the third heat exchanger, to heat the SOEC unit, and to feed the fourth heat exchanger with a first stream, in that order; and to sequentially feed the second heat exchanger and the first heat exchanger with a second stream, in that order. In another exemplary embodiment of the preferred embodiment, the heated intermediate fluid is split into three streams. A first stream is used to sequentially feed the third heat exchanger, heat the SOEC unit, and feed the fourth heat exchanger, in that order. A second stream is used to feed the first heat exchanger, and a third stream is used to preheat the second heat exchanger.

[0098] In a preferred embodiment, the system may comprise the tertiary heat exchanger. The tertiary heat exchanger may heat or preheat the water source or the steam source using at least part of the heat of the hydrogen-containing stream, thereby cooling the at least part of hydrogen-containing steam and producing a cooled hydrogen-containing steam.

[0099] In some embodiments, the tertiary heat exchanger may heat the water source or the steam source to produce a saturated gaseous steam or superheated gaseous steam at a temperature lower than the steam stream temperature. The temperature of the saturated gaseous steam or superheated gaseous steam may be in the range of about 20°C to about 150°C below the steam stream temperature. A preferred temperature may be in any one of the following ranges: about 20°C to about 140°C, about 20°C to about 120°C, about 20°C to about 100°C, about 20°C to about 80°C, about 20°C to about 60°C, about 20°C to about 40°C, about 20°C to about 30°C below the steam stream temperature. In that case, the one or more heat exchangers may comprise the fourth heat exchanger, and the tertiary heat exchanger may be upstream of the fourth heat exchanger. The saturated gaseous steam or superheated gaseous steam produced by the tertiary heat exchanger may then be heated in the fourth heat exchanger to produce the steam stream to be fed to the SOEC unit at the steam stream temperature.

[0100] In some embodiments, the system further may comprise a water or steam recovering means for recovering water or steam from the cooled hydrogen-containing stream downstream of the tertiary heat exchanger.

[0101] In some embodiments, the system may be configured to use at least part of the recovered water or steam as at least part of the water source or steam source.

[0102] In some embodiments, the system may be configured to directly use at least part of the cooled hydrogen-containing stream as at least part of the fuel.

[0103] In some embodiments, the system may further comprise a hydrogen recovering means for recovering hydrogen gas from at least a part of the cooled hydrogencontaining stream downstream of the tertiary heat exchanger, thereby producing a recovered hydrogen gas.

[0104] In some embodiments, the system may be configured to use at least part of the recovered hydrogen gas as at least part of the fuel.

[0105] In some embodiments, the system may be configured to use at least part of the hydrogen-containing stream to feed the SOEC unit along with the steam stream at the steam stream temperature.

[0106] In some embodiments, the system may comprise a quinary heat exchanger downstream of the hydrogen recovering means. The quinary heat exchanger may preheat at least part of the recovered hydrogen gas by using at least part of the heat of the hydrogen-containing stream, thereby producing preheated recovered hydrogen gas. In that case, the one or more heat exchangers may further comprise a fifth heat exchanger. The fifth heat exchanger may heat the preheated recovered hydrogen gas to a temperature that is equal to the steam stream temperature, thereby producing heated recovered hydrogen gas. The system may then be configured touse the heated recovered hydrogen gas to feed the SOEC unit along with the steam stream at the steam stream temperature.

[0107] In some embodiments, the system may comprise the quaternary heat exchanger. The quaternary heat exchanger may heat or preheat the water source or the stream source using at least part of the heat of the oxygen-containing stream or the quaternary heat exchanger may preheat the cool oxygen-containing carrier gas using at least part of the heat of the oxygen-containing steam, thereby cooling the at least part of oxygen-containing steam and producing a cooled oxygen-containing steam.

[0108] In the case where the quaternary heat exchanger heats the water source or the stream source using at least part of the heat of the oxygen-containing steam, the quaternary heat exchanger may produce a saturated gaseous steam or superheated gaseous steam at a temperature lower than the steam stream temperature. The temperature of the saturated gaseous steam or superheated gaseous steam may be in the range of about 20°C to about 100°C below the oxygen-containing stream temperature. A preferred temperature may be in any one of the following ranges: about 20°C to about 90°C, about 20°C to about 80°C, about 20°C to about 70°C, about 20°C to about 60°C, about 20°C to about 50°C, about 20°C to about 40°C below the oxygen-containing stream temperature. The one or more heat exchangers may then comprise the fourth heat exchanger, the fourth heat exchanger being downstream of the quaternary heat exchanger. The saturated gaseous steam or superheated gaseous steam at a temperature lower than the steam stream temperature may then be heated in the fourth heat exchanger to produce the steam stream to be fed to the SOEC unit at the steam stream temperature.

[0109] In a preferred embodiment, the system may comprise the tertiary heat exchanger and quaternary heat exchanger. In that case, the tertiary heat exchanger may be downstream of the quaternary heat exchanger. The quaternary heat exchanger may heat the water source or the stream source by using at least part of the heat of the oxygen-containing steam, thereby cooling the at least part of oxygen-containing steam and producing a cooled oxygen-containing steam. The quaternary heat exchanger may thus produce a saturated gaseous steam or a first superheated gaseous steam at a temperature lower than the steam stream temperature. Thetemperature of the saturated gaseous steam or first superheated gaseous steam may be in the range of about 20°C to about 100°C below the oxygen-containing stream temperature. A preferred temperature may be in any one of the following ranges: about 20°C to about 90°C, about 20°C to about 80°C, about 20°C to about 70°C, about 20°C to about 60°C, about 20°C to about 50°C, about 20°C to about 40°C below the oxygen-containing stream temperature. The tertiary heat exchanger may then heat the saturated gaseous steam or first superheated gaseous steam to produce a superheated gaseous steam or a second superheated gaseous steam at a temperature lower than the steam stream temperature, but higher than the saturated gaseous steam or first superheated gaseous temperature produced by the quaternary heat exchanger. The temperature of the superheated gaseous steam or second superheated gaseous steam may be in the range of about 20°C to about 150°C below the hydrogen-containing stream temperature, provided that it is higher than the temperature of the saturated gaseous steam or first superheated gaseous steam. A preferred temperature may be in any one of the following ranges: about 20°C to about 140°C, about 20°C to about 120°C, about 20°C to about 100°C, about 20°C to about 80°C, about 20°C to about 60°C, about 20°C to about 40°C below the hydrogen-containing stream temperature. The one or more heat exchangers may then comprise the fourth heat exchanger, the fourth heat exchanger being downstream of tertiary heat exchanger and the quaternary heat exchanger. The second superheated gaseous steam at a temperature lower than the steam stream temperature may then be heated in the fourth heat exchanger to produce the steam stream to be fed to the SOEC unit at the steam stream temperature.

[0110] In the case where the quaternary heat exchanger preheats the cool oxygencontaining carrier gas, the quaternary heat exchanger may produce a preheated oxygen-containing carrier gas. The temperature of the cool oxygen-containing carrier gas is as defined above. The temperature of the preheated oxygen-containing carrier gas may be in the range of about 20°C to about 170°C below the oxygen-containing carrier gas temperature. A preferred temperature may be in any one of the following ranges: about 20°C to about 160°C, about 20°C to about 140°C, about 20°C to about 120°C, about 20°C to about 100°C, about 20°C to about 80°C, about 20°C to about 60°C below the oxygen-containing stream temperature. The one or more heat exchangers may then comprise the third heat exchanger, the third heat exchangerbeing downstream of the quaternary heat exchanger. The third heat exchanger may heat the preheated oxygen-containing carrier gas to produce the oxygen-containing carrier gas to be fed to the SOEC unit at the oxygen-containing carrier gas temperature.

[0111] The temperature of the cooled oxygen-containing stream may be in the range of about room temperature to about 200°C, preferably room temperature to about 180°C, more preferably room temperature to about 100°C, and even more preferably room temperature to about 60°C.

[0112] In some embodiments, the system may further comprise an oxygen recovering means for recovering oxygen gas from at least part of the cooled oxygen-containing stream.

[0113] In some embodiments, the system may be configured to use at least part of the recovered oxygen gas as at least part of the oxidant.

[0114] In some embodiments, the system may be configured to directly use at least part of the cooled oxygen-containing stream as at least part of the oxidant.

[0115] In some embodiments, the one or more secondary heat exchangers further may comprise the first heat exchanger, the second heat exchanger, the third heat exchanger, the fourth heat exchanger, and the fifth heat exchanger. In one embodiment of these embodiments, the heated intermediate fluid may be split into a plurality of streams to heat the one or more secondary heat exchangers, i.e. , to preheat the fuel via the first heat exchanger, to preheat the oxidant via the second heat exchanger, to heat the oxygen-containing carrier gas via the third heat exchanger, to heat the water source or the steam source via the fourth heat exchanger, and to heat the recovered hydrogen gas, and, optionally to heat the SOEC unit. In another embodiment, the heated intermediate fluid may be used to sequentially feed to one or more secondary heat exchangers and, optionally, to heat the SOEC unit. The sequence may be adjusted to minimize the number and / or size of heat exchangers and extract maximum heat from the heated intermediate fluid without violating thermodynamic temperature cross over. In one exemplaryT1 embodiment, the heated intermediate fluid is used to feed the third heat exchanger, to feed the fourth heat exchange^ to heat the SOEC unit, to feed the fifth heat exchanger, the second heat exchanger and the first heat exchanger, in that order. In still another embodiment, the heated intermediate fluid may be split into one or more streams to sequentially feed at least a one of the one or more heat exchangers (and, optionally, heat the SOEC unit) with one stream, and feed the other one(s) of the one or more heat exchangers with the remaining stream(s). The sequence of feeding the at least one of the one or more secondary heat exchangers and, optionally, heating the SOEC unit with one stream may be adjusted to minimize the number and / or size of heat exchangers and extract maximum heat from the heated intermediate fluid without violating thermodynamic temperature cross over. As such, sequentially feeding at least one of the one or more heat exchangers and, optionally, heating the SOEC unit with one stream may comprise feeding the third heat exchanger, feeding the fourth heat exchanger, feeding the fifth heat exchanger, and, optionally heating the SOEC unit in any sequential order, while feeding the other one(s) of the one or more heat exchangers may comprise feeding the second heat exchanger and feeding the first heat exchanger. According to one embodiment, the remaining stream(s) may comprise one stream to be used to feed the second heat exchanger and to feed the first heat exchanger, in that order. According to another embodiment, the remaining stream(s) may comprise two streams to be used to feed the first heat exchanger and to feed the second heat exchanger, separately. In one exemplary embodiment, the heated intermediate fluid is split into two streams to sequentially feed the third heat exchanger, to heat the SOEC unit, and to feed the fifth heat exchanger and fourth heat exchanger with a first stream, in that order; and to sequentially feed each of the second heat exchanger and first heat exchanger with a second stream, in that order. In another exemplary embodiment, the heated intermediate fluid is split into three streams. A first stream is used to sequentially feed the third heat exchanger, to heat the SOEC unit, and to feed the fifth heat exchanger and the fourth heat exchanger, in that order. A second stream is used to feed the first heat exchanger, and a third stream is used to feed the second heat exchanger.

[0116] In some embodiments, the system may be used in a glass manufacturing process or in the cement manufacturing process.

[0117] In some embodiments, the system may be configured to use at least part of the recovered hydrogen gas in the glass manufacturing process or the cement manufacturing process.

[0118] In some embodiments, the system may be used in a float glass manufacturing process and may further comprise a tin bath chamber.

[0119] In some embodiments, the system may be configured to use at least part of the recovered hydrogen gas to feed the atmosphere of the tin bath chamber.

[0120] In some embodiments, one or more separators, compressors and / or coolers may be installed in order to compress and / or to further cool down the different fluids downstream the heat exchangers. In a preferred embodiment, one or more separators, compressors and / or coolers may be installed downstream the tertiary heat exchanger to further cool down the cooled hydrogen-containing stream.

[0121] In some embodiments, the one or more secondary heat exchangers may provide the whole energy to heat the different sources, gases, or streams to their predetermined temperature. In some other embodiments, one or more secondary heat exchangers may provide only the partial energy needed to heat the different sources, gases, or streams to their predetermined temperature, that is, higher than 0% to less than 100%, preferably between more than 0% to about 30%, more preferably between more than 0% to about 20%, and even more preferably between more than 0% to about 10% of the total power needed for each source, gas, or stream. In that case, the remaining energy may be provided by electrical heating.

[0122] Other aspects of the present invention include a system of using a SOEC unit and an intermediate fluid heated by flue gas to produce or recover hydrogen gas and / or oxygen gas to be used in a manufacturing process including a combustion reaction, a system for producing or recovering, and delivering hydrogen gas and / or oxygen gas to a combustion chamber using a SOEC unit and an intermediate fluid heated by flue gas, a system for producing or recovering hydrogen gas and / or oxygen gas and of using produced or recovered hydrogen gas and / or oxygen gas, a system forproducing or recovering hydrogen gas and / or oxygen gas, a system of using a SOEC unit and an intermediate fluid heated by flue gas to produce a hydrogen-containing stream and / or an oxygen-containing stream to be directly fed to a combustion chamber, a system of producing and directly feeding a hydrogen-containing stream and / or an oxygen-containing stream to a combustion chamber using a SOEC unit and an intermediate fluid heated by flue gas, a system for manufacturing a glass article or a cement article, or a system for preparing a float glass article. The invention according to these aspects may include one or more components described in the invention according to the second aspect.

[0123] Other aspects of the present invention include a method of using a SOEC unit and an intermediate fluid heated by flue gas to produce or recover hydrogen gas and / or oxygen gas, preferably to be used in a manufacturing process including a combustion reaction, a method for producing or recovering, and delivering hydrogen gas and / or oxygen gas to a combustion chamber using a SOEC unit and an intermediate fluid heated by flue gas, a method for producing or recovering hydrogen gas and / or oxygen gas and of using produced or recovered hydrogen gas and / or oxygen gas, a method for producing or recovering hydrogen gas and / or oxygen gas, a method of using a SOEC unit and an intermediate fluid heated by flue gas to produce a hydrogen-containing stream and / or an oxygen-containing stream to be directly fed to a combustion chamber, a method of producing and directly feeding a hydrogen-containing stream and / or an oxygen-containing stream to a combustion chamber using a SOEC unit and an intermediate fluid heated by flue gas, a method for manufacturing a glass article or a cement article, or a method for preparing a float glass article. The invention according to these aspects may include one or more of the steps described in the invention according to the first aspect.

[0124] The system may suitably be used in the implementation of one of the above mentioned embodiments of the first aspect of the present disclosure or other aspects of the present disclosure including a method of using a SOEC unit and an intermediate fluid heated by flue gas to produce or recover hydrogen gas and / or oxygen gas, preferably to be used in a manufacturing process including a combustion reaction, a method for producing or recovering, and delivering hydrogen gas and / or oxygen gas to a combustion chamber using a SOEC unit and anintermediate fluid heated by flue gas, a method for producing or recovering hydrogen gas and / or oxygen gas and of using produced or recovered hydrogen gas and / or oxygen gas, a method for producing or recovering hydrogen gas and / or oxygen gas, a method for manufacturing a glass article or a cement article, or a method for preparing a float glass article.BRIEF DESCRIPTION OF DRAWINGS

[0125] The following figures provide preferred embodiments for illustrating the description and should not be seen as limiting the scope of invention.

[0126] Fig. 1 provides a schematic diagram of a first exemplary embodiment.

[0127] Fig. 2 provides a schematic diagram of a second exemplary embodiment.

[0128] Fig. 3 provides a schematic diagram of a third exemplary embodiment.

[0129] Fig. 4 illustrates the technical feasibility of integrating SOEC, HeatOx™ and combustion.

[0130] Fig. 5 provides a schematic diagram of a fourth exemplary embodiment.DESCRIPTION OF SPECIFIC EMBODIMENTS

[0131] Embodiments of the present disclosure, which are briefly summarized above and explained in greater detail below, can be understood by reference to the illustrative embodiments of the disclosure depicted in the drawings, which are not necessarily to scale. The illustrative embodiments depicted are intended only as exemplary and are therefore not to meant to limit the scope of the invention.

[0132] The following detailed description should be read with reference to the drawings.

[0133] Fig. 1 illustrates a first exemplary embodiment of the present invention. According to this first exemplary embodiment, a fuel (CHU) 116 and an oxidant, for example, an oxygen gas (O2) 117, are provided and preheated in, respectively, a first heat exchanger 2HX1 to about 450°C and a second heat exchanger 2HX2 to about 550°C before being fed to a furnace FN. Raw glass materials 121 are provided in a melting chamber MC and heated via the combustion reaction of the preheated fuel 119 with the preheated oxidant 118 in the furnace FN. Flue gas (FG, 102) is generated at a temperature of about 1500 °C. At least part of the heat of the flue gas (FG, 102) exiting the furnace FN is transferred to an intermediate fluid (for example air, 130) at room temperature via a primary heat exchanger 1 HX, thereby producing a heated intermediate fluid 103. The temperature of the heated intermediate fluid 103 exiting the primary heat exchanger 1 HX is in the range of about 875°C to about 925°C, while the temperature of the flue gas 134 exiting the primary heat exchanger 1 HX is about 550°C. The heated intermediate fluid 103 is used to feed the plurality of secondary heat exchangers comprising the first heat exchanger 2HX1 , the second heat exchanger 2HX2, a third heat exchanger 2HX3, and a fourth heat exchanger 2HX4 and to heat a Solid Oxide Electrolyzer Cells (SOEC) unit 105 to a SOEC operating temperature of about 850°C. In the third heat exchanger 2HX3, an oxygen-containing carrier gas 104 at a temperature in the range of room temperature to about 200°C is heated to an oxygen-containing carrier gas temperature of about 850°C before being fed to the SOEC unit 105. In the fourth heat exchanger 2HX4, a steam stream 106 at steam stream temperature of about 850°C to be fed to the SOEC unit 105 is produced. More specifically, the heated intermediate fluid 103 is used to feed sequentially the third heat exchanger 2HX3, to partially or wholly heat the SOEC unit 105, to feed the fourth heat exchanger 2HX4, the second heat exchanger 2HX2, and the first heat exchanger 2HX1 , in that order. At the exit of the first heat exchanger 2HX1 , the intermediate fluid cooled by heat exchange (125) is recycled. An oxygencontaining stream 107 and a hydrogen-containing stream 108 are produced by the SOEC unit 105. In this first exemplary embodiment, the oxygen-containing stream 107 is allowed to vent off, while a tertiary heat exchanger 3HX upstream of the fourth heat exchanger is provided to heat a water source 109 provided at a temperature of about 20°C-25°C using at least part of the heat of the hydrogen-containing stream 108, thereby cooling the at least part of hydrogen-containing steam 108 andproducing a cooled hydrogen-containing steam 110. The temperature of the cooled hydrogen-containing stream 110 exiting the tertiary heat exchanger 3HX is about 70°C. A superheated steam 131 at a temperature of about 100°C to a maximum of about 830°C is produced by the tertiary heat exchanger. Water and hydrogen gas are recovered from the cooled hydrogen-containing stream 110 downstream of the tertiary heat exchanger 3HX by a H2O / H2 separator S1 , thereby producing recovered water 112 and a recovered hydrogen gas 113. At least part of the recovered water 112 is then used as at least part of the water 109. At least another part of the water source may be directly provided (114). Between the tertiary heat exchanger 3HX and the H2O / H2 separator S1 , compressors (C1) and / or further coolers (C2) may be installed in order to compress and / or to further cool down the cooled hydrogencontaining stream 110 to room temperature. At least part of the recovered hydrogen gas 113a is used as a source for feeding the atmosphere of a tin bath in a float glass manufacturing process.

[0134] Fig. 2 illustrates a second exemplary embodiment of the present invention. Compared to the first exemplary embodiment, as the fuel, instead of natural gas (CH4), this embodiment uses a mix of hydrogen gas and natural gas (CH4) 216. In addition, instead of being used to sequentially feed the secondary heat exchangers, the heated intermediate fluid (air) 203 is split into three streams (203a, 203b, 203c) to sequentially feed the third heat exchanger 2HX3, to partially or wholly heat the SOEC unit 205, and to feed the fourth heat exchanger 2HX4 with one stream 203b, and separately feed the first heat exchanger 2HX1 with stream 203 a and the second heat exchanger 2HX2 with stream 203c. The intermediate fluid cooled by heat exchange is recycled at the exit of each of the first, second, and fourth heat exchanger (225a, 225c, 225b). Furthermore, compared with the first exemplary embodiment, a quaternary heat exchanger 4HX is also provided upstream of the tertiary heat exchanger 3HX to heat the water 209 using at least part of the oxygencontaining stream 207 produced by the SOEC unit 205 thereby cooling the at least part of oxygen-containing stream and producing a cooled oxygen-containing stream 226 at a temperature of about 125°C. A saturated steam 231 at a temperature of about 100°C to a maximum of about 830°C is produced by the quaternary heat exchanger 4HX. The cooled oxygen-containing stream 226 is directly used as at least part of the oxidant 229. Compared with the first exemplary embodiment, thetemperature of the cooled hydrogen-containing stream 210 exiting the tertiary heat exchanger 3HX is about 125°C and a superheated stream 232 is produced by the tertiary heat exchanger 3HX before being fed to the fourth heat exchanger and producing the steam stream 206 at the steam stream temperature of about 850°C. As in the first exemplary embodiment, water and hydrogen gas are recovered from the cooled hydrogen-containing stream 210 downstream of the tertiary heat exchanger 3HX by a H2O / H2 separator S1 , thereby producing recovered water 212 and a recovered hydrogen gas 213. At least part of the recovered water 212 is then used as at least part of the water source 209. At least part of the recovered hydrogen gas 213a is used to feed the atmosphere of a tin bath in a float glass manufacturing process as in the first exemplary embodiment. Compared with the first exemplary embodiment, at least another part of the recovered hydrogen gas 213b is used as at least part of the fuel.

[0135] Fig. 3 illustrates a third exemplary embodiment of the present invention. Compared with the second exemplary embodiments, the heated intermediate fluid (for example air) 303 is split into five streams (303a, 303b, 303c, 303d, 303e) to partially or wholly heat the SOEC unit 305 and to feed the plurality of secondary heat exchangers including the first heat exchanger 2HX1 , the second heat exchanger 2HX2, the third heat exchanger 2HX3, and the fourth heat exchanger 2HX4, separately. The intermediate fluid cooled by heat exchange (225a, 225b, 225c, 225d, 225e) is recycled at the exit of each of the first, second, third, and fourth heat exchanger.

[0136] Fig. 5 illustrates a fourth exemplary embodiment of the present invention. Compared with the third exemplary embodiment, an external steam source at about 125°C is provided as the steam source 509 and is directly preheated in the quaternary heat exchanger 4HX to produce the steam stream to be fed to the SOEC unit 505. In addition, the cooled oxygen-containing stream is directly used as the only source of oxidant and water recovered from the H2O / H2 separator S1 is discarded.

[0137] Electrical heat transfer or heating power may be provided to different components of the systems, such as the melting chamber and the SOEC unit, as indicated by the Q (electrical heat transfer) and W (heating power) arrows. Electrical power may also be provided to the SOEC unit.

[0138] Flue gas is liberated from combustion of fuel and glass raw material decomposition and mainly comprises CO2, H2O and traces of suspended particulate matter (SPM, e.g., silicon oxides). In order to avoid the potential risk of deposition of SPM in the heat exchanger, the flue gas is always kept above 550°C.

[0139] Inasmuch as the present invention is subject to many variations, modifications and changes in detail, it is intended that the subject matter discussed above and shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense.EXAMPLES

[0140] Comparative Example 1Today, the most developed technology for float glass furnaces is based on NG / Air combustion. Table 1 shows the combustion data collected by Air Liquide. In this scheme, the air is preheated for combustion from about 25°C to about 1200°C by heat exchange, whereas the flue gas leaves the melting chamber at about 1778°C.

[0141] Table 1

[0142] Table 2 shows the CO2 emissions data collected (data for combustion) and calculated (data for combustion) by Air Liquide. CO2 emissions are estimated under the assumption that natural gas is composed only of CH4.

[0143] Table 2

[0144] Hereinafter, data highlighted in bold, i.e. , the total heat required for glass melting and the losses, will remain constant along all the evaluated scenarios due to technical restrictions in float glass manufacturing processes, such as melting chamber design, thermal isolation, cullet load, etc.

[0145] Comparative Example 2The prior art float furnace configuration fed with natural gas and air (NG / Air) of Comparative Example 1 is used as a base model to estimate the performance for the natural gas oxy-com bustion (NG / O2) combustion.

[0146] Table 3 shows an NG / O2 energy equivalent scenario based on NG / Air combustion. O2 flow is adjusted in a way to obtain the same O2 concentration (molar) in the flue gas as in the NG / Air case. 6410 Nm3 / h of O2 in Table 3 are equivalent to 220 tpd (tons per day) of O2. Nowadays, NG / O2 combustion is considered as a tentative approach to reduce the CO2 emissions from float glass manufacturing processes. However, some techno-economic issues at the combustion chamber limit its implementation on a large scale.

[0147] Table 3

[0148] Table 4 shows the CO2 emissions for the NG / O2 energy equivalent scenario. CO2 emissions are estimated under the assumption that natural gas is composed only of CH4.

[0149] Table 4

[0150] Comparative Example 3Recent advances in the flat glass process have reduced the operation temperature from about 1700°C to about 1800°C to close to about 1500 °C. In this direction, Table 5 shows a “benchmark scenario” instead of the one calculated from the energy equivalent at about 1778 °C.

[0151] Table 5

[0152] Table 6 shows the CO2 emissions for the NG / O2 energy equivalent scenario at about 1500°C operation temperature. CO2 emissions are estimated under the assumption that natural gas is composed only of CH4.

[0153] Table 6

[0154] Example 1This example corresponds to the first exemplary embodiment illustrated in the schematic diagram of Fig. 1 and shows SOEC / HeatOx™ integration for producing only the H2 required to feed the tin bath (150 Nm3 / h) in a float glass manufacturing process. This example will not take into account the heat recovery from SOEC oxygen-containing stream because the amount of heat available from flue gas islarge enough to generate the small amount of the steam up to about 850°C required to produce the target H2. Moreover, installing a heat exchanger for a small heat transfer is not cost-wise. However, heat recovery from the SOEC hydrogencontaining stream is needed to drive H2 / H2O separation. This configuration demands an SOEC system of 0.54 MW size currently available in the market. In Table 7, 5555 Nm3 / h of O2 in Table 3 are equivalent to about 190 tpd of O2.

[0155] In this scheme, the furnace is fed with NG / O2 and the entire amount of produced H2 is used to feed only the atmosphere of the tin bath. Since the oxygen-containing stream generated from SOEC is not a significant amount compared to O2 required for combustion (<1.5 vol%), it can be vented off. A hot air stream as the heated intermediate fluid could be fed in series to all the heat exchanger units while still maintaining the sufficient driving force for heat transfer. Roughly 29% of the air heat is used to preheat carrier gas up to about 850°C, generate steam up to about 850°C and for preheating fuel and oxygen.

[0156] Table 7

[0157] Table 8 shows the CO2 emissions in the NG / O2 / HeatOx™ scenario at 1500 °C operation temperature in the case of feeding the entire produced H2 to the atmosphere of the tin bath.

[0158] Table 8

[0159] As can be seen from Table 8, the integration scheme of Example 1 is able to reduce up to 4.4% (wt%) of annual CO2 emissions from the float glass manufacturing process in comparison with the benchmark scenario of Comparative Example 3.

[0160] Advantageously, it was confirmed by this scenario the annual CO2 emissions of a process involving a combustion reaction can already be reduced by simple integration of a SOEC unit and the use of hydrogen produced by the SOEC unit in at least a part of the process, for example to feed the tin bath in a float glass manufacturing process.

[0161] Example 2This example corresponds to the second exemplary embodiment illustrated in schematic diagram of Fig. 2. It considers SOEC integration for producing the H2 required to feed the tin bath (150 Nm3 / h) and to feed the furnace to make NG / H2 fuel mix ratio to 35 / 65 vol% such that contribution of H2 to total combustion heat is roughly 35%. A portion of heat is recovered from SOEC downstream gases to preheat the steam to intermediate temperatures before reaching up to about 850°C. This configuration demands installation of a 11.3 MW SOEC unit. In Table 9, 5237 Nm3 / h of 02 are equivalent to 179.6 tpd of O2.

[0162] Table 9

[0163] Table 10 shows the CO2 emissions in the NG / H2 / O2 / HeatOx™ scenario at about 1500°C operation temperature using produced H2 to feed the atmosphere of the tin bath and for 35% combustion heat.

[0164] Table 10

[0165] Combined CO2 emissions from combustion and glass raw material decomposition could be reduced by roughly 28% (wt %) by switching from the benchmark scheme. Roughly 31 mol% of the total O2 required for combustion could be supplied by SOEC. The hot air stream has to be split to feed the secondary heat exchangers to provide sufficient driving force for heat transfer. Roughly 54% of the process air heat is used to preheat carrier gas up to 850 °C, generate steam up to 850°C and for preheating the fuel and oxygen.

[0166] Advantageously, it was confirmed by this scenario that the annual CO2 emissions of a process involving a combustion reaction can be further reduced by the integration of a SOEC unit and the use of hydrogen produced by the SOEC unit in at least a part of the process, for example to feed the tin bath in a float glass manufacturing process, and as at least a part of the fuel for the combustion reaction.

[0167] Example 3This example corresponds to the third exemplary embodiment illustrated in the schematic diagram of Fig. 3. This case corresponds to the critical scenario with the maximum thermal integration between SOEC, HeatOx™ and float glass combustion chamber. The process feasibility threshold is evaluated by using a standard process simulator commonly used in the industry, for example Aspen Plus™ or Aspen Custom Modeler™. The results show that the heat content in the flue gas is insufficient to feed a SOEC unit and produce the required H2 to completely replace NG. The threshold NG / H2 mixing ratio in the proposed integration is when the contribution of H2 produced by the SOEC unit to total combustion heat is roughly 65% (see Fig. 4). This is equivalent to a NG / H2 volume mix ratio of 14 / 86. Roughly a 75% of the air heat is used after all heat transfer operations listed in (1) to (5).(1)Heat the steam stream feed to SOEC unit to about 850°C;(2)Heat the SOEC unit to 850°C at the time of start-up;(3)Heat the oxygen-containing carrier gas to feed to SOEC unit to about 850 °C;(4)Heat the oxidant (O2) feed to the combustion chamber (furnace) to about 550 °C.(5)Heat the fuel feed to the combustion chamber (furnace) to about 450 °C.

[0168] In Table 11 , 4957 Nm3 / h of O2 are equivalent to 171 tpd of O2.

[0169] The configuration at threshold limit demands installation of a 20.4 MW SOEC unit.

[0170] Table 11

[0171] Table 12 shows the CO2 emissions in the NG / H2 / O2 / HeatOx™ scenario at about 1500 °C operation temperature using produced H2 to feed the atmosphere of the tin bath and for 65% combustion heat.

[0172] Table 12

[0173] Combined CO2 emissions from combustion and glass raw material decomposition could be reduced by roughly 47% (wt %) by switching from benchmark configuration to the threshold limit NG / H2 / O2 / SOEC / HeatOx™ configuration. Roughly 60%(mol) of the total O2 required for combustion could be supplied by SOEC saving roughly 97 tpd of makeup O2.

[0174] Advantageously, it was confirmed that the annual CO2 emissions of a process involving a combustion reaction can be further reduced by the integration of a SOEC unit and the use of hydrogen produced by the SOEC unit in at least a part of the process, for example to feed the tin bath in a float glass manufacturing process, and as at least a part of the fuel for the combustion reaction, in addition to the use of oxygen produced by the SOEC unit as at least a part of the oxidant for the combustion reaction.

[0175] Example 4This example corresponds to the fourth exemplary embodiment illustrated in schematic diagram of Fig. 5. This scenario considers the full supply of low-carbon H2 from SOEC and the free access to an external steam source at about 125 °C. Controlling factor is the full H2 supply to the combustion chamber and float glass for using as a protective atmosphere. A very limited amount of O2 will be supplied externally for sweep purposes. In this scenario, as shown in Fig. 5, the steam inlet is injected directly into the quaternary heat exchanger 4HX whereas the recovered water from H2O / H2 unit is discarded. This scenario is useful to indicate the maximum low-carbon H2 and O2 that can be supplied with no gas storage.

[0176] Table 13

[0177] Table 14 shows the CO2 emissions in the NG / H2 / O2 / HeatOx™ scenario at 1500 °C operation temperature using produced H2 to feed the atmosphere of the tin bath and for 100% combustion heat in the case of a free steam provided at 125 °C.

[0178] Table 14

[0179] Combined CO2 emissions from combustion and glass raw material decomposition could be reduced by roughly 69% (wt %) by switching from benchmark configuration of Comparative Example 3 to a full supply of low-carbon H2 and O2 generated at the SOEC unit.

[0180] Advantageously, it was confirmed that the annual CO2 emissions of a process involving a combustion reaction can be further reduced when there is access to steam source at about 125 °C compared with the scenario of Example 3, since hydrogen can fully replace the natural gas as the fuel for the combustion reaction.

[0181] Table 15 is a summary of the different scenarios of Examples 1-4 showing the required H2 and O2 for combustion, as well as the required H2 for the tin bath, the H2 and O2 produced by the SOEC unit, as well as the fuel and oxygen saved, and CO2 reduction compared with the benchmark scenario of Comparative Example 3.

[0182] Table 15

[0183] Advantageously, Example 1 already shows advantages with respect to NG savings, O2 savings and decreases of CO2 emissions compared with the benchmark scenario of Comparative Example 3 (NG / O2 feed at 25°C). These savings are due to the HeatOx™ integration (NG / O2 feed at 450°C / 550°C) improving the combustion efficiency.

[0184] As shown in Table 15 in Examples 2-4, increased use of hydrogen produced by the SOEC unit as fuel for the combustion in replacement of NG leads to an increase ofthe O2 savings and decreases of the CO2 emissions, and thus to a further improvement of the combustion efficiency.

[0185] Accordingly, it was confirmed by the scenarios of the above Examples that the integration of high temperature Solid Oxide Electrolysis Cell (SOEC) in processes involving combustion reactions, for example float glass manufacturing processes, is an effective method to valorize the released high grade waste heat and reduce the CO2 emissions by replacing the NG / Air combustion by a low-carbon H2 / O2 combustion fed from the SOEC. Moreover, it was confirmed that the thermal integration between SOEC and HeatOx™ units can enhance the efficiency in the combustion process and push forward the reduction of CO2 footprint in the industry.

[0186] While the invention has been described in conjunction with specific embodiments thereof, it is obvious that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as falling within the spirit and scope of the appended claims. The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. Furthermore, it can be recognized by those skilled in the art that certain steps can be combined into a single step.REFERENCE SIGNS LIST

[0187] 100, 200, 300, 500: Exemplary systems of the present invention102, 202, 302, 502: Fuel gas (FG)103, 203, 203a, 203b, 203c, 303, 303a, 303b, 303c, 303d, 303e, 503, 503a, 503b,503c, 503d, 503e: Heated intermediate fluid104, 204, 304, 504: Cool oxygen-containing carrier gas105, 205, 305, 505: SOEC unit106, 206, 306, 506: Steam stream107, 207, 307, 507: Oxygen-containing stream108, 208, 308, 508: Hydrogen-containing stream109, 209, 309: Water or steam source509: Steam source at about 125°C110, 210, 310, 510: Cooled hydrogen-containing gas112, 212, 312: Recovered water or steam113, 213, 313, 513; Recovered hydrogen gas113a, 213a, 313a, 513a: Recovered hydrogen gas sent to tin bath atmosphere213b, 313b, 513b: Recovered hydrogen gas to be used as fuel114, 214, 314: External source of water116, 216, 316, 516: External source of CH4for fuel117, 217, 317: External source of O2 for oxidant118, 218, 318, 518: preheated oxidant119: preheated fuel121 , 221 , 321 , 521 : Float glass raw materials and cullets (RM)122, 222, 322, 522: Melted glass sent to float glass123, 223, 323, 523: Oxygen-containing carrier gas125, 225a, 225b, 225c, 325a, 325b, 325c, 325d, 325c, 525a, 525b, 525c, 525d,525e: Cold intermediate fluid (air) to recycle226, 326, 526: Cooled oxygen-containing gas227, 327, 527: Fuel228, 328, 528: preheated fuel229, 329: O2 for oxidant130, 230, 330, 530: Intermediate fluid (air)131 , 231 , 331 , 531 : Saturated steam below the steam stream temperature232, 332, 532: Superheated gaseous steam below the steam stream temperature134, 234, 334, 534: Cooled flue gasRM: Float glass raw materials and culletsMC: Melting chamberFN: Furnace102: Flue gas (FG)1 HX: Primary heat exchanger2HX1 : First heat exchanger2HX2: Second heat exchanger2HX3: Third heat exchanger2HX4: Fourth heat exchanger3HX: Tertiary heat exchanger4HX: Quaternary heat exchangerC1 : CompressorC2: CoolerS1 : H2 / H2O separatorQmeit: Heat transfer from furnace to melting chamber (kW)QF OSS: Heat loss from furnace and melting chamber (kW)QF.eiec: Electrical heat transfer to melting chamber (kW)WE, eieC: Electrical power to SOEC unit (kW)QE.eiec: Heat loss from SOEC unit (kW)WC1 : Duty for compressor C1 (kW)QC2: Heat duty for cooler C2 (kW)

Claims

CLAIMS1. A method of using flue gas heat resulting from a combustion reaction, comprising: a) providing a fuel and an oxidant; b) preheating the fuel and the oxidant to produce a preheated fuel and a preheated oxidant; c) feeding the preheated fuel and preheated oxidant to a combustion chamber; d) heating raw materials via the combustion reaction of the preheated fuel with the preheated oxidant in the combustion chamber and generating flue gas; e) transferring at least part of the heat of the flue gas exiting the combustion chamber to an intermediate fluid, thereby producing a heated intermediate fluid; f) heating a Solid Oxide Electrolyzer Cells (SOEC) unit to a SOEC operating temperature; g) exchanging heat using at least part of the heat of the heated intermediate fluid; h) providing a steam stream at a steam stream temperature and an oxygencontaining carrier gas at an oxygen-containing carrier gas temperature, and feeding the steam stream and the oxygen-containing carrier gas to the SOEC unit to produce an oxygen-containing stream and a hydrogen-containing stream; wherein exchanging heat comprises:

1. preheating the fuel to produce the preheated fuel to be fed to the combustion chamber and / or2. preheating the oxidant to produce the preheated oxidant to be fed to the combustion chamber.

2. The method according to claim 1 , wherein heating the SOEC unit to the SOEC operating temperature is performed partially or wholly by using at least part of the heat of the heated intermediate fluid.

3. The method according to claim 1 or 2, further comprising:- providing a cool oxygen-containing carrier gas at a temperature lower than the oxygen-containing carrier gas temperature, wherein exchanging heat further comprises heating the cool oxygen-containing carrier to produce the oxygen-containing carrier gas to be fed to the SOEC unit at the oxygen-containing carrier gas temperature.

4. The method according to any one of claims 1 to 3, further comprising- providing a water source or a steam source at a temperature lower than the steam stream temperature, wherein exchanging heat further comprises heating the water source or the steam source to produce the steam stream to be fed to the SOEC unit at the steam stream temperature.

5. The method according to any one of claims 1 to 4, wherein using at least part of the heat of the heated intermediate fluid comprises- splitting the heated intermediate fluid into a plurality of streams for exchanging heat and, optionally, for heating the SOEC unit, or- sequentially exchanging heat and, optionally, heating the SOEC unit, preferably, wherein the intermediate fluid is air.

6. The method according to any one of claims 1 to 5, further comprising:- heating or preheating the water source or the steam source by using at least part of the heat of the hydrogen-containing stream, thereby cooling the hydrogen-containing stream and producing a cooled hydrogen-containing stream.

7. The method according to claim 6, further comprising- directly using at least part of the cooled hydrogen-containing stream as at least part of the fuel.

8. The method according to claim 6, further comprising:- recovering water or steam from at least a part of the cooled hydrogen-containing stream, thereby producing recovered water or steam, and- using at least part of the recovered water or steam as at least part of the water source or steam source.

9. The method according to claim 6 or 8, further comprising- recovering hydrogen gas from at least a part of the cooled hydrogen-containing stream, thereby producing a recovered hydrogen gas.

10. The method according to claim 9, further comprising using at least part of the recovered hydrogen gas as at least part of the fuel.11 . The method according to any one of claims 8 to 10, further comprising:- feeding at least part of the hydrogen-containing stream to the SOEC unit along with the steam stream at the steam stream temperature, or- preheating at least part of the recovered hydrogen gas by using at least part of the heat of the hydrogen-containing stream, thereby producing preheated recovered hydrogen gas, wherein exchanging heat further comprises heating the preheated recovered hydrogen gas to the steam stream temperature, thereby producing heated recovered hydrogen gas, and- feeding the heated recovered hydrogen gas to the SOEC unit along with the steam stream.

12. The method according to any one of claims 1 to 11 , further comprising- heating or preheating the water source or steam source or preheating the cool oxygen-containing carrier gas by using at least part of the heat of the oxygencontaining stream, thereby cooling the oxygen-containing steam and producing a cooled oxygen-containing stream.

13. The method according to claim 12, further comprising- recovering oxygen gas from at least part of the cooled oxygen-containing stream, thereby producing recovered oxygen gas, and- using at least part of the recovered oxygen gas as at least part of the oxidant, or- directly using at least part of the cooled oxygen-containing stream as at least part of the oxidant.

14. The method according to any one of claims 8 to 13, wherein the raw materials are glass raw materials, the method further comprising:- using at least part of the recovered hydrogen gas in a glass manufacturing process, preferably to feed the atmosphere of a float bath in a float glass manufacturing process.

15. A system of using flue gas heat from a combustion reaction, comprising:- a Solid Oxide Electrolyzer Cells (SOEC) unit operable to a SOEC operating temperature to produce an oxygen-containing stream and a hydrogen-containing stream, wherein the SOEC unit is configured to receive a steam stream at a steam stream temperature and an oxygen-containing carrier gas at oxygen-containing carrier gas temperature,- a primary heat exchanger for transferring at least part of the heat of flue gas to an intermediate fluid to produce a heated intermediate fluid, the flue gas being produced by the combustion reaction for heating raw materials and exiting a combustion chamber;- one or more secondary heat exchangers comprising a first heat exchanger for preheating a fuel to produce the preheated fuel to be fed to the combustion chamber; and / or a second heat exchanger for preheating an oxidant to produce the preheated oxidant to be fed to the combustion chamber; and / or a third heat exchanger for heating a cool oxygen-containing carrier gas at a temperature lower than the oxygen-containing carrier gas temperature to produce the oxygen-containing carrier gas to be fed to the SOEC unit; and / or a fourth heat exchanger for heating a water source or a steam source to produce the steam stream to be fed to the SOEC unit;-optionally, a tertiary heat exchanger for heating or preheating the water source or the steam source using at least part of the heat of the hydrogen-containing stream, and / or a quaternary heat exchanger for heating or preheating the water source or the steam source using at least part of the heat of the oxygen-containing stream and / or for preheating the cool oxygen-containing carrier gas, wherein the system is configured to use at least part of the heat of the heated intermediate fluid for exchanging heat in the one or more secondary heat exchangers.

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