Integration of solid oxide electrolysis cells (SOEC) and oxygen purificator to enhance high temperature processes

Abstract

The present disclosure relates to a method for producing a purified oxygen-containing stream, the method comprising: heating a Solid Oxide Electrolyzer Cells (SOEC) unit to a SOEC operating temperature; providing a water source or a steam source at a water source or steam source temperature; heating the water source or the steam source to produce a steam stream at a steam stream temperature; providing a sweep gas at a sweep gas temperature; feeding the steam stream and the sweep gas to the SOEC unit to produce an oxygen-containing stream and a hydrogen-containing stream; cooling the oxygen-containing stream to a temperature in the range of about 20°C to about 100°C, preferably about 40°C to about 60°C, more preferably about 44°C to about 55°C, and even more preferably about 50°C; and, after the cooling step, purifying the oxygen-containing stream to produce the purified oxygen-containing stream The present disclosure also relates a system for producing a purified oxygen-containing stream.

Description

Integration of solid oxide electrolysis cells (SOEC) and oxygen purificator to enhance high temperature processesTECHNICAL FIELD

[0001] The present disclosure relates to methods and systems for producing a purified oxygen-containing stream, in particular methods and systems using Solid Oxide Electrolyzer Cells (SOEC) and an oxygen purificator to produce a purified oxygen-containing stream. The present disclosure also relates to methods and systems for combusting a fuel, as well as methods and systems for heating raw materials.BACKGROUND ART

[0002] High temperature steam electrolyzers, such Solid Oxide Electrolyzer Cells (SOEC, operating temperature of about 600°C to about 1000°C) are capable of delivering hydrogen and oxygen gases with a relatively low carbon footprint, depending on the electricity used in the process, qualifying them as low-carbon hydrogen and oxygen gases.

[0003] Theoretically, a SOEC unit can deliver hydrogen and steam at the cathode and pure oxygen at the anode. However, in practice, it can deliver pure hydrogen only after a downstream water separation process, whereas pure oxygen has to be diluted with air for easy and safe handling at high temperatures. Usually, the delivered oxygen and air mixture (O2 / N2 with O2>20.95%) is discarded into the atmosphere.

[0004] The O2 / N2 mixture produced by the anode of the SOEC unit can be qualified as “clean”, meaning that it contains a very low amount of pollutants.

[0005] As oxygen is widely used in several industrial applications, such as oxyacetylene welding, metal refining, ceramic processing and especially incombustion, it would be of interest to valorize the clean oxygen-enriched O2 / N2 mixture obtained from a SOEC unit.SUMMARY OF INVENTION

[0006] The inventors have found that, by integrating such a SOEC unit and an oxygen purificator, purified oxygen could be produced with improved efficiency, notably by reduction of the power input to the oxygen purificator. Moreover, the inventors have found that the integration of a SOEC unit and an oxygen purificator into a high-temperature process releasing waste heat and demanding hydrogen and / or oxygen for operation, such as combustion, could be beneficial for valorizing waste heat, enhancing efficiency of the process, and decreasing the carbon footprint, notably by providing the total or partial amount of low- carbon hydrogen and oxygen used in the high-temperature process.

[0007] Thus, the present disclosure relates to a method for producing a purified oxygen-containing stream according to claim 1 , a method of combusting a fuel according to Claim 7, a method of heating raw materials according to Claim 14, and a system for producing a purified oxygen-containing stream according to claim 15. Advantageous embodiments may include features of dependent claims.Definitions

[0008] The singular forms “a”, “an” and “the” include plural referents, unless the context clearly dictates otherwise.

[0009] “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.

[0010] “Providing” in this description and in the claims 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.

[0011] “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.

[0012] 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 that another embodiment is from the one particular value and / or to the other particular value, along with all combinations within said range.

[0013] 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.

[0014] 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.

[0015] It should be noted that in specifying any range of temperature, any upper temperature can be associated with any lower temperature.

[0016] The term “and / or” includes the meanings “and”, “or” and also all the other possible combinations of the elements connected to this term.

[0017] As used herein, the term “air” is used to mean dry air comprising about 20.95vol% of oxygen.

[0018] 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

[0019] As used herein, the term “hydrogen-containing stream” is used to mean a stream comprising hydrogen. The hydrogen-containing stream may also comprise steam.

[0020] As used herein, the “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 substantially be free of water or steam.

[0021] 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.

[0022] 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.

[0023] 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, air, oxygen enriched air, pure oxygen (as defined in the industry), oxygen gas as defined above, anoxygen-containing stream, a purified oxygen-containing stream as defined below or combinations thereof.

[0024] 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.

[0025] 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.

[0026] As used herein, the term “water source” is used to mean a water reservoir at liquid phase.

[0027] 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 operating temperature).

[0028] 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.

[0029] As used herein, the term “steam stream temperature” is used to mean the SOEC operating temperature.Description of the invention

[0030] In a first aspect, the present disclosure relates to a method for producing a purified oxygen-containing stream, the method comprising:- heating a Solid Oxide Electrolyzer Cells (SOEC) unit to a SOEC operating temperature;- providing a water source or a steam source at a water source or steam source temperature,- heating the water source or the steam source to produce a steam stream at a steam stream temperature;- providing a sweep gas at a sweep gas temperature;- feeding the steam stream and the sweep gas to the SOEC unit to produce an oxygen-containing stream and a hydrogen-containing stream;- cooling the oxygen-containing stream to a temperature in the range of about 20°C to about 100°C, preferably about 40°C to about 60°C, more preferably about 44°C to about 55°C, and even more preferably about 50°C; and- after the cooling step, purifying the oxygen-containing stream to produce the purified oxygen-containing stream.

[0031] The SOEC operating temperature and the steam stream temperature may be in the range of about 600°C to about 850°C, preferably about 600°C to about 750°C, more preferably about 600°C to about 750°C.

[0032] The sweep gas temperature, the temperature of the oxygen-containing stream and the hydrogen-containing stream are the same as the SOEC operating temperature and the steam stream temperature.

[0033] In some embodiments, the water source is a 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, more preferably room temperature to about 80°C. The steam source is a saturated or superheated gaseous steam reservoir at a 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.

[0034] In some embodiments, cooling the oxygen-containing stream may comprise transferring at least part of the heat of the oxygen-containing stream to a sweepgas source to produce an intermediate sweep gas at an intermediate sweep gas temperature lower than the sweep gas temperature. In that case, the method may further comprise heating the intermediate sweep gas at the intermediate sweep gas temperature to produce the sweep gas at the sweep gas temperature.

[0035] In some embodiments, cooling the oxygen-containing stream may further comprise another cooling step, for example using a chiller unit or exchanging heat with another part of the system.

[0036] In some embodiments, the sweep gas source temperature may be in the range between room temperature to about 60°C, preferably in the range from room temperature to about 50°C.

[0037] In some embodiments, the intermediate sweep gas temperature may be in the range of about 20°C to about 150°C below the sweep gas 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 sweep gas temperature.

[0038] In some embodiments, heating the water source or the steam source to produce the steam stream at the steam stream temperature or heating the intermediate sweep gas at the intermediate sweep gas temperature to produce the sweep gas at the sweep gas temperature may be performed purely electrically. In some other embodiments, these may be performed wholly or partially by heat exchange from an external medium. In that case, the external medium may be a flue gas or an intermediate fluid.

[0039] Heating the intermediate sweep gas at the intermediate sweep gas temperature to produce the sweep gas at the sweep gas temperature or heating the water source or the steam source to produce the steam stream at the steam stream temperature partially by using at an external medium means that the externalmedium may provide partially the power necessary for heating the intermediate sweep gas at the intermediate sweep gas temperature to produce the sweep gas at the sweep gas temperature or for heating the water source or the steam source to produce a steam stream at a steam stream 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 intermediate sweep gas at the intermediate sweep gas temperature to produce the sweep gas at the sweep gas temperature or to heat the water source or the steam source to produce a steam stream at a steam stream temperature.

[0040] Heating the intermediate sweep gas at the intermediate sweep gas temperature to produce the sweep gas at the sweep gas temperature or heating the water source or the steam source to produce a steam stream at a steam stream temperature wholly by using the external medium means that the external medium may provide for 100% of the power necessary for heating the intermediate sweep gas at the intermediate sweep gas temperature to produce the sweep gas at the sweep gas temperature or for heating the water source or the steam source to produce a steam stream at a steam stream temperature.

[0041] In some embodiments, the sweep gas may be air or oxygen enriched air comprising an oxygen content higher than air. The oxygen enriched air may comprise higher than about 20.95 vol% of oxygen, preferably at least about 23 vol%, more preferably at least about 24 vol%, even more preferably at least about 26 vol%, and still even more preferably at least about 28 vol% of oxygen. The sweep gas may be substantially free of water or steam.

[0042] In some embodiments, the sweep gas also may be an inert gas, such as nitrogen or argon. In that case, in order to keep the oxygen-containing stream produced by the SOEC unit at a certain oxygen concentration, a flow rate of thesweep gas should be adjusted for the SOEC unit and the step of purifying oxygen-containing stream to be operated in a good manner.

[0043] In some embodiments, the oxygen-containing stream may comprise higher than about 20.95 vol% of oxygen, 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.

[0044] 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 hydrogen-containing 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.

[0045] Purifying the oxygen-containing stream means separating the oxygen gas from other gas or gases contained in the oxygen-containing stream.

[0046] In some embodiments, the purified oxygen-containing stream may comprise 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.

[0047] In some embodiments, heating the SOEC unit to a SOEC operating temperature may be performed partially or wholly by using an external medium such as an intermediate fluid. In some other embodiments, heating the SOEC unit to the SOEC operating temperature may be performed purely electrically.

[0048] Heating the SOEC unit to the SOEC operating temperature partially by using an external medium means that the external medium 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 representbetween 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 unit to the SOEC operating temperature.

[0049] Heating the SOEC unit to the SOEC operating temperature wholly by using the external medium means that the external medium may provide for 100% of the power necessary for heating the SOEC unit to the SOEC operating temperature.

[0050] In some embodiments, the method may further comprise, after the cooling step and before the purifying step, mixing an external source of air with the cooled oxygen-containing stream.

[0051] In some embodiments, the external source of air may be provided at a temperature in the range of room temperature to about 50°C, preferably at room temperature.

[0052] In some embodiments, the mixture of the external source of air and the cooled oxygen-containing stream may then comprise higher than about 20.95 vol% of oxygen, 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.

[0053] In some embodiments, the mixture of the external source of air and the cooled oxygen-containing stream may be at a temperature in the range of room temperature to about 60°C, more preferably room temperature to about 50°C.

[0054] 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.

[0055] In some embodiments, the method may further comprise recovering hydrogen gas from at least a part of the hydrogen-containing stream, thereby producing arecovered hydrogen gas.

[0056] A second aspect of the present disclosure relates to a method of combusting a fuel, the method comprising:- heating a Solid Oxide Electrolyzer Cells (SOEC) unit to a SOEC operating temperature;- providing a water source or a steam source at a water source or steam source temperature,- heating the water source or the steam source to produce a steam stream at a steam stream temperature;- providing a sweep gas at a sweep gas temperature;- feeding the steam stream and the sweep gas to the SOEC unit to produce an oxygen-containing stream and a hydrogen-containing stream;- cooling the oxygen-containing stream to a temperature in the range of about 20°C to about 100°C, preferably about 40°C to about 60°C, more preferably about 44°C to about 55°C, and even more preferably about 50°C; and- after the cooling step, purifying the oxygen-containing stream to produce the purified oxygen-containing stream; and- feeding the fuel and the purified oxygen-containing stream as part of an oxidant to a combustion chamber for combusting the fuel, wherein combusting the fuel with the oxidant generates a flue gas.

[0057] In some embodiments, the method of the second aspect may include the embodiments according to the method of the first aspect.

[0058] In some embodiments, the combustion chamber may be a furnace.

[0059] In typical commercial furnaces, the flue gas is typically and preferably hot, having a temperature ranging from about 1000°C 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.

[0060] In some embodiments, the method may further comprise using at least part of the hydrogen-containing stream as at least part of the fuel.

[0061] In some embodiments, the method may further comprise using the recovered hydrogen gas as at least part of the fuel.

[0062] In some embodiments, the method may be a continuous method. A continuous method means that the method is repeated. As such, the method may further comprise:- 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.

[0063] The intermediate fluid is preferably clean, non-toxic, non-combustible, and substantially non-corrosive. Further, the intermediate fluid must be capable of being heated to a temperature in the range of about 600 °C to about 1600 °C in a heat transfer means by the flue gas. Preferred fluids include gases such as air, nitrogen, carbon dioxide, water vapor, and the like. Other preferred fluids include liquids, such as water, glycols, and the like, including mixtures of the same. Air is a particularly preferred intermediate fluid for use in the present invention.

[0064] 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.

[0065] 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 heated intermediate fluid. In this case, the heated intermediate fluid may thus be the external medium as explained above. In some other embodiments, heating the SOEC unit to the SOEC operating temperature maybe performed purely electrically.

[0066] Heating the SOEC unit to the SOEC operating temperature partially or wholly by using at least part of the heat of the heated intermediate fluid is as explained above for the first aspect when using an external medium.

[0067] In some embodiments, the method further may comprise recovering an inert gas such as nitrogen or argon from the oxygen-containing stream when purifying the oxygen-containing stream. The recovered inert gas may then be reused as at least part of the sweep gas in a closed loop with an optional additional make-up gas.

[0068] In some embodiments where cooling the oxygen-containing stream comprises transferring at least part of the heat of the oxygen-containing stream to a sweep gas source to produce the intermediate sweep gas at the intermediate sweep gas temperature lower than the sweep gas temperature, the method may further comprise heating the intermediate sweep gas at an intermediate sweep gas temperature to produce the sweep gas at the sweep gas temperature, wherein heating the intermediate sweep gas at an intermediate sweep gas temperature to produce the sweep gas at the sweep gas temperature is performed by exchanging heat using at least part of the heat of the heated intermediate fluid.

[0069] In some embodiments, heating the water source or the steam source to produce the steam stream at the steam stream temperature may be performed by exchanging heat using at least part of the heat of the heated intermediate fluid.

[0070] In some embodiments, cooling the oxygen-containing stream may further comprise transferring to the water source or the steam source at least part of the heat of the oxygen-containing stream obtained after the heat transfer that produces the intermediate sweep gas, thereby producing preheated water or preheated steam at an intermediate water temperature or intermediate steamtemperature lower than a saturation temperature. Heating the water source or the steam source to produce the steam stream at the steam stream temperature may then comprise the following steps:- producing the preheated water or preheated steam as mentioned above; and- heating the preheated water or the preheated steam to produce the steam stream to be fed to the SOEC unit at the steam stream temperature by exchanging heat using at least part of the heat of the heated intermediate fluid.

[0071] In some embodiments, heating the water source or the steam source may comprise 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. Using at least part of the heat of the hydrogencontaining stream may then comprise directly heating the water source or the steam source, or, alternatively, heating the preheated water or preheated steam source at an intermediate water temperature or intermediate steam temperature lower than a saturation temperature 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 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. Heating the water source or the steam source to produce the steam stream at the steam stream temperature may then comprise the following steps:- optionally producing the preheated water or preheated steam as mentioned above;- heating the preheated water or preheated steam, or directly heating the water source or the steam source by using at least part of the heat of the hydrogencontaining stream, to produce a saturated gaseous steam or superheated gaseous steam; and- heating the saturated gaseous steam or superheated gaseous steam byexchanging heat using at least part of the heated intermediate fluid to produce the steam stream to be fed to the SOEC unit at a steam stream temperature.

[0072] 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, even more preferably about 50°C to about 120°C.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] In some embodiments, the recovered hydrogen gas may be recovered from at least part of the cooled hydrogen-containing stream.

[0077] In some embodiments, the method may further comprise preheating the recovered hydrogen gas by using at least part of the heat of the hydrogencontaining stream, thereby producing preheated recovered hydrogen gas. In that case, the preheated recovered hydrogen gas may be heated to a temperature equal to the steam stream temperature by exchanging heat using at least part of the heat of the heated intermediate fluid, 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.

[0078] 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 ofstreams for exchanging heat and, optionally, for heating the SOEC unit. In a preferred embodiment, exchanging heat may comprise heating the intermediate sweep gas to produce the sweep gas, and heating the water source or the steam source to produce the steam stream. In one exemplary embodiment of the preferred embodiment, the plurality of streams may be used to heat the intermediate sweep gas to produce the sweep gas, to heat the water source or the steam source to produce the steam stream, and to heat the SOEC unit.

[0079] In some 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 heating the intermediate sweep 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 intermediate sweep gas, the SOEC unit, and to heat the water source or the steam source, in that order.

[0080] For all the above-mentioned aspects, in some embodiments, exchanging heat may provide the whole power to heat the different sources, gases, or streams to their predetermined temperatures. In some other embodiments, exchanging heat may provide only part of the power needed to heat the different sources, gases, or streams to their predetermined temperatures, 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 power may be provided by electrical heating.

[0081] A third aspect of the present disclosure relates to a method of heating raw materials, the method comprising:- heating a Solid Oxide Electrolyzer Cells (SOEC) unit to a SOEC operatingtemperature;- providing a water source or a steam source at a water source or steam source temperature,- heating the water source or the steam source to produce a steam stream at a steam stream temperature;- providing a sweep gas at a sweep gas temperature;- feeding the steam stream and the sweep gas to the SOEC unit to produce an oxygen-containing stream and a hydrogen-containing stream;- cooling the oxygen-containing stream to a temperature in the range of about 20°C to about 100°C, preferably about 40°C to about 60°C, more preferably about 44°C to about 55°C, and even more preferably about 50°C;- after the cooling step, purifying the oxygen-containing stream to produce the purified oxygen-containing stream;- feeding the fuel and the purified oxygen-containing stream as part of an oxidant to a combustion chamber for combusting the fuel, wherein combusting the fuel with the oxidant generates flue gas; and- heating the raw materials with the heat generated by combusting the fuel with the oxidant.

[0082] In some embodiments, the method of the third aspect may include the embodiments according to the method of the first aspect or the second aspect.

[0083] 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.

[0084] A fourth aspect of the present disclosure relates to a system for producing a purified oxygen-containing stream, the system comprising:- a Solid Oxide Electrolyzer Cells (SOEC) unit operable at 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 a sweep gas at a sweep gas temperature;- one or more oxygen-containing stream heat exchangers, and optionally a chiller unit, downstream of the SOEC unit to cool the oxygencontaining stream produced by the SOEC unit to a temperature in the range of about 20°C to about 100°C, preferably about 40°C to about 60°C, more preferably about 44°C to about 55°C, and even more preferably about 50°C, and- an oxygen purificator downstream of the one or more oxygencontaining stream heat exchangers, and optionally the chiller unit, configured to purify the oxygen-containing stream, thereby producing a purified oxygencontaining stream.

[0085] The oxygen purificator may use adsorption, permeation or cryogenic technology. Examples of such purificators may include VSA (Vacuum Swing Adsorption) systems, ASU (Air Separation Unit) systems and oxygen generation systems utilizing cryogenic distillation. The purificator may split the oxygencontaining stream into i) a purified oxygen containing stream whose oxygen content is higher than the oxygen content in the oxygen-containing stream and ii) a separated sweep gas whose oxygen content is noticeably similar to the oxygen content in the oxygen-containing stream.

[0086] Exemplary materials for the one or more oxygen-containing stream heat exchangers may be ferritic steels, Ni-based alloys or ceramics.

[0087] The SOEC operating temperature, the steam stream, the sweep gas, the hydrogen-containing stream, the oxygen-contain stream, as well as their respective temperatures are as defined above.

[0088] In some embodiments, the system is configured to heat a water source or asteam source to produce the steam stream at the steam stream temperature.

[0089] The water source and the steam source, as well as their respective temperatures are as defined above.

[0090] In some embodiments, the one or more oxygen-containing stream exchangers comprise a first oxygen-containing stream heat exchanger. The first oxygencontaining stream exchanger may be configured to transfer at least part of the heat of the oxygen-containing stream to a sweep gas source to produce an intermediate sweep gas at an intermediate sweep gas temperature lower than the sweep gas temperature. The system may then further be configured to heat the intermediate sweep gas at the intermediate sweep gas temperature to produce the sweep gas at the sweep gas temperature.

[0091] The sweep gas source and the intermediate sweep gas, as well as their respective temperatures are as defined above.

[0092] In some embodiments, heating the water source or a steam source to produce the steam stream at the steam stream temperature and heating the intermediate sweep gas at the intermediate sweep gas temperature to produce the sweep gas at the sweep gas temperature may be performed purely electrically. In some other embodiments, these may be performed wholly or partially with a heat exchanger using an external medium. In that case, the external medium may be flue gas or an intermediate fluid.

[0093] Partially or wholly heating the water source or a steam source to produce the steam stream at the steam stream temperature or partially or wholly heating the intermediate sweep gas at the intermediate sweep gas temperature to produce the sweep gas at the sweep gas temperature using an external medium is as defined above.

[0094] In some embodiments, the purified oxygen-containing stream at the outlet of the oxygen purificator may comprise at least about 80 vol%, preferably at leastabout 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.

[0095] In some embodiments, the system may further be configured to use an external medium 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.

[0096] Partially or wholly heating the SOEC unit to the SOEC operating temperature using an external medium is as defined above.

[0097] In some embodiments, the system may be configured to deliver an external source of air between the one or more oxygen-containing stream heat exchangers (and optionally the chiller unit) and the oxygen purificator to be mixed with the cooled oxygen-containing stream. In that case, the external source of air is as defined above.

[0098] In some embodiments, the system may be configured to feed at least part of the hydrogen-containing stream to the SOEC unit along with the steam stream at the steam stream temperature.

[0099] In some embodiments, the system may further comprise a hydrogen recovering means for recovering hydrogen gas from at least a part of the hydrogencontaining stream, thereby producing recovered hydrogen gas.

[0100] A fifth aspect of the present disclosure relates to a system for combusting a fuel, the system comprising:- a Solid Oxide Electrolyzer Cells (SOEC) unit operable at a SOEC operating temperature to produce an oxygen-containing stream and a hydrogencontaining stream, wherein the SOEC unit is configured to receive a steam stream at a steam stream temperature and a sweep gas at a sweep gas temperature;- one or more oxygen-containing stream heat exchangers, and optionally a chiller unit, downstream of the SOEC unit to cool the oxygencontaining stream produced by the SOEC unit to a temperature in the range of about 20°C to about 100°C, preferably about 40°C to about 60°C, more preferably about 44°C to about 55°C, and even more preferably about 50°C,- an oxygen purificator downstream of the one or more oxygen-containing stream heat exchangers, and optionally the chiller unit, configured to purify the oxygen-containing stream, thereby producing a purified oxygen-containing stream; and- a combustion chamber to be fed with a fuel and the purified oxygencontaining stream as part of an oxidant for combusting the fuel.

[0101] In some embodiments, the system of the fifth aspect may include the embodiments according to the system of the fourth aspect.

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

[0103] 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.

[0104] In some embodiments, the system may further include 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 of the fuel and the oxidant and exiting the combustion chamber.

[0105] The flue gas, the intermediate fluid, the heated intermediate fluid, as well as their respective temperatures are as defined above.

[0106] 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 theSOEC unit to the SOEC operating temperature. In some other embodiments, the system may further be configured to heat the SOEC unit purely electrically.

[0107] 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.

[0108] In some embodiments, the oxygen purificator may be configured to recover an inert gas such as nitrogen or argon from the oxygen-containing stream. As mentioned above, the recovered inert gas may then be reused as at least part of the sweep gas in a closed loop with an optional additional make-up gas.

[0109] In some embodiments, the system may further comprise one or more secondary heat exchangers, 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.

[0110] In some embodiments, the one or more secondary heat exchangers may comprise a first heat exchanger for heating the intermediate sweep gas at an intermediate sweep gas temperature to produce the sweep gas at the sweep gas temperature.

[0111] In some embodiments, the one or more secondary heat exchangers may comprise a second heat exchanger.

[0112] In some embodiments, the system may then be configured to heat the water source or the steam source to produce the steam stream at the steam stream temperature via the second heat exchanger.

[0113] In some embodiments, the one or more oxygen-containing stream heat exchangers may further comprise a second oxygen-containing stream heat exchanger downstream the first oxygen-containing stream heat exchanger. The second oxygen-containing stream may be configured to transfer at least part ofthe heat of the oxygen-containing stream exiting the first oxygen-containing stream heat exchanger to the water source or the steam source to produce preheated water or preheated steam at an intermediate water temperature or intermediate steam temperature lower than a saturation temperature. The second oxygen-containing stream heat exchanger may also be upstream of the second heat exchanger in relation to the water / steam flow, so that the system may be configured to heat the water source or the steam source to produce the steam stream at the steam stream temperature by:- producing the preheated water or preheated steam via the second oxygencontaining stream exchanger;- heating the preheated water or preheated steam via the second heat exchanger to produce the steam stream to be fed to the SOEC unit at a steam stream temperature.

[0114] In some embodiments, the system may comprise a tertiary heat exchanger upstream of the second heat exchanger configured to use at least part of the heat of the hydrogen-containing stream to heat the water source or the steam source, thereby cooling the at least part of hydrogen-containing stream and producing a cooled hydrogen-containing stream as defined here above. The tertiary heat exchanger may then be configured to directly heat the water source or the steam source in the tertiary heat exchanger. Alternatively, the tertiary heat exchanger may be between the second heat exchanger and the second oxygen-containing stream heat exchanger (i.e., upstream of the second heat exchanger and downstream of the oxygen-containing stream heat exchanger) to heat the preheated water or preheated steam source produced by the second oxygen-containing heat exchanger to produce a saturated gaseous steam or superheated gaseous steam at a temperature lower than the steam stream temperature. The system may then be configured to heat the water source or the steam source to produce the steam stream at the steam stream temperature by:- optionally producing the preheated water or preheated steam via the second oxygen-containing stream exchanger;- heating the preheated water or preheated steam produced by the secondoxygen-containing stream exchanger via the tertiary heat exchanger, or directly heating the water source or the steam source, via the tertiary heat exchanger to produce a saturated gaseous steam or superheated gaseous steam; and- heating the saturated gaseous steam or superheated gaseous steam via the second heat exchanger to produce the steam stream to be fed to the SOEC unit at a steam stream temperature.

[0115] In some embodiments, the system further may comprise a water or steam recovering means for recovering water or steam from the cooled hydrogencontaining stream downstream of the tertiary heat exchanger.

[0116] 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.

[0117] 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.

[0118] In some embodiments, the hydrogen recovering means may be downstream of the tertiary heat exchanger.

[0119] In some embodiments, the system may comprise a quaternary heat exchanger downstream of the hydrogen recovering means. The quaternary heat exchanger may preheat 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 third heat exchanger. The third heat exchanger may be placed downstream of the quaternary heat exchanger and 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 to use the heated recovered hydrogen gas to feed the SOEC unit along with the steam stream at the steam stream temperature.

[0120] In some embodiments, the heated intermediate fluid is split into a plurality ofstreams 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 and the second heat exchanger. In an exemplary embodiment, the heated intermediate fluid is split to heat the intermediate sweep gas via the first heat exchanger, the water source or the steam source via the second heat exchanger, and to heat the SOEC unit.

[0121] 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 and the second heat exchanger. In one exemplary embodiment of the preferred embodiment, the heated intermediate fluid is used to feed the first heat exchanger, to heat the SOEC unit, and to feed the second heat exchanger, in that order.

[0122] In some embodiments, the one or more secondary heat exchangers may provide the whole power to heat the different sources, gases, or streams to their predetermined temperatures. In some other embodiments, one or more secondary heat exchangers may provide only part of the power needed to heat the different sources, gases, or streams to their predetermined temperatures, 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 power may be provided by electrical heating.

[0123] A sixth aspect of the present disclosure relates to a system for heating raw materials, the system comprising:- a Solid Oxide Electrolyzer Cells (SOEC) unit operable at a SOEC operating temperature to produce an oxygen-containing stream and a hydrogencontaining stream, wherein the SOEC unit is configured to receive a steam stream at a steam stream temperature and a sweep gas at a sweep gas temperature;- one or more oxygen-containing stream heat exchangers, and optionally a chiller unit, downstream of the SOEC unit to cool the oxygencontaining stream produced by the SOEC unit to a temperature in the range of about 20°C to about 100°C, preferably about 40°C to about 60°C, more preferably about 44°C to about 55°C, and even more preferably about 50°C,- an oxygen purificator downstream of the one or more oxygen-containing stream heat exchangers, and optionally the chiller unit, configured to purify the oxygen-containing stream, thereby producing a purified oxygen-containing stream,- a combustion chamber to be fed with a fuel and the purified oxygencontaining stream as part of an oxidant for combusting the fuel; and- a melting chamber for heating raw materials to a melting temperature with the heat generated by combusting the fuel with the oxidant.

[0124] In some embodiments, the system of the sixth aspect may include the embodiments according to the system of the fourth aspect or the system of the fifth aspect.

[0125] Other aspects of the present disclosure include a method of using a SOEC unit and an oxygen purificator, a method for enhancing the efficiency of purification of an oxygen-containing stream, a method for enhancing the efficiency of a combustion reaction. These aspects may include one or more of the steps described in the invention according to the first aspect, the second aspect, or the third aspect.

[0126] Other aspects of the present disclosure include a system of using a SOEC unit and an oxygen purificator, a system for enhancing the efficiency of purification of an oxygen-containing stream, a system for enhancing the efficiency of acombustion reaction. These aspects may include one or more components described in the invention according to the fourth aspect, the fifth aspect, or the sixth aspect.

[0127] Another aspect of the present disclosure includes a method using the system of any of the above aspects.BRIEF DESCRIPTION OF DRAWINGS

[0128] The following figures provide preferred embodiments for illustrating the description and should not be seen as limiting the scope of invention.

[0129] Fig. 1 provides a schematic diagram of a first exemplary embodiment.

[0130] Fig. 2 provides a schematic diagram of a second exemplary embodiment.

[0131] Fig. 3 provides a schematic diagram of a third exemplary embodiment.

[0132] Fig. 4 provides a schematic diagram of a fourth exemplary embodiment.

[0133] Fig. 5 shows specific energy consumption as a function of the oxygen concentration in air (vol %) in the case of VSA (Vacuum Swing Adsorption).

[0134] Figs. 6a, 6b, 6c, and 6d show, respectively, VSA (Vacuum Swing Adsorption) power input, natural gas consumption, direct CO2 emissions, oxygen consumption as a function of the different scenarios.DESCRIPTION OF SPECIFIC EMBODIMENTS

[0135] 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 notnecessarily to scale. The illustrative embodiments depicted are intended only as exemplary and are therefore not to meant to limit the scope of the invention.

[0136] The following detailed description should be read with reference to the drawings.

[0137] Fig. 1 illustrates a first exemplary embodiment of the present invention. According to this exemplary embodiment, a water source 101 at room temperature is provided and heated in a first heat exchanger 1 HX to produce a steam stream 102 at a steam stream temperature of about 750°C. The first heat exchanger 1 HX may use waste heat provided by an intermediate medium or electricity. A sweep gas source 104, which is a N2 / O2 mixture, is also provided at room temperature, heated in an oxygen-containing stream exchanger SHX1 to produce an intermediate sweep gas 105 at an intermediate sweep gas temperature of about 720°C before being further heated to produce a sweep gas 106 at a sweep gas temperature, which is the same as the steam stream temperature. The steam stream 102 and the sweep gas 106 are fed to an SOEC unit 107. The SOEC unit 107 is heated to a SOEC operating temperature, which is the same as the steam stream temperature and sweep gas temperature, either by electricity and / or an external source of heat. A hydrogen-containing stream 108 and an oxygen-containing stream 109 are produced by the SOEC unit 107. At least part of the hydrogen-containing stream 108a may optionally be recycled to be fed to the SOEC unit 107 along with the steam stream 102 at the steam stream temperature. The other part of the hydrogen-containing stream 108b may be used to recover hydrogen gas or to be fed to some other parts of the system, for example, as part of a fuel for combustion (not illustrated). The oxygen-containing stream 109 is cooled in a first oxygen-containing stream heat exchanger SHX1 to a temperature of about 180°C. The oxygen-containing stream cooled by the first oxygen-containing stream heat exchanger SHX1 may then be further cooled by using chiller units (not illustrated) or in a second oxygen-containing stream heat exchanger (not illustrated) to a temperature of about 60°C, thus producing a cooled oxygencontaining stream. An external source of air 111 is provided at roomtemperature and mixed with the cooled oxygen-containing stream 110. The mixture of the cooled oxygen-containing stream and air 112 is fed to a VSA (Vacuum Swing Adsorption) unit 113 which serves as an oxygen purificator separating O2 and a separated sweep gas (115), mainly comprising N2, thereby producing a purified oxygen-containing stream 114. The purified oxygencontaining stream 217 comprises about 80 vol% to about 99.8 vol% of oxygen.

[0138] Fig. 2 illustrates a second exemplary embodiment of the present invention. According to this exemplary embodiment, a make-up fuel (for example, CH4) 201 and make-up oxidant (for example, O2) at start-up (not illustrated) are provided before being fed to a combustion chamber / furnace FN. Raw glass materials 202 are provided in a melting chamber MC and heated via the combustion reaction of the fuel 221 with the oxidant in the furnace FN. Flue gas 203 (FG) is generated at a temperature of about 1500°C. At least part of the heat of the flue gas 203 (FG) exiting the furnace FN is transferred to an intermediate fluid 204 (for example, air) at room temperature via a primary heat exchanger 1 HX, thereby producing a heated intermediate fluid 205. The temperature of the heated intermediate fluid 205 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 206 exiting the primary heat exchanger 1 HX is about 550 °C. The heated intermediate fluid 205 is split (205a and 205b) and used to feed a plurality of secondary heat exchangers comprising a first heat exchanger 2HX1 , and a second heat exchanger 2HX2, and, optionally to heat a SOEC unit 207 to a SOEC operating temperature of about 750°C (not illustrated). A sweep gas source 208, which is a N2 / O2 mixture, at room temperature is provided and heated in a first oxygen-containing stream heat exchanger SHX1 to produce an intermediate sweep gas 209 at an intermediate sweep gas temperature of about 720°C.The intermediate sweep gas 209 is heated to produce a sweep gas 210 at a sweep gas temperature of about 750°C by the first heat exchanger 2HX1 . A water source 211 at room temperature is provided and then heated in a second heat exchanger 2HX2 to produce the steam stream 212 at the steam stream temperature. The steam stream 212 and the sweep gas 210 are fed to the SOEC unit 207. The SOECunit 207 is heated to the SOEC operating temperature, which is the same as the steam stream temperature and sweep gas temperature either by using at least part of the heat of the heated intermediate fluid 205 or by using electricity or a combination of both. A hydrogen-containing stream 213 and an oxygencontaining stream 214 are produced by the SOEC unit 207. At least part of the hydrogen-containing stream 213a may optionally be recycled to be fed to the SOEC unit 207 along with the steam stream 212 at the steam stream temperature and / or at least part of the hydrogen-containing stream 213b may optionally be fed directly to the furnace FN / com bustion chamber as at least part of the fuel 221. The oxygen-containing stream 214 is cooled in the first oxygencontaining stream heat exchanger SHX1 to a temperature of about 180°C. The oxygen-containing stream cooled by the first oxygen-containing stream heat exchanger SHX1 may then be further cooled by using chiller units (not illustrated) to a temperature of about 60°C, thus producing a cooled oxygencontaining stream 215. An eternal source of air (not shown) may be optionally provided and mixed with the cooled oxygen-containing stream 215. The cooled oxygen-containing stream 215 or mixture of the cooled oxygen-containing stream 215 and air is fed to a VSA (Vacuum Swing Adsorption) unit 216 which serves as an oxygen purificator separating N2 and O2, thereby producing a purified oxygen-containing stream 217. The purified oxygen-containing stream 217 comprises about 80 vol% to about 99.8 vol% of oxygen. The purified oxygen-containing stream 217 is fed directly to the furnace FN / combustion chamber as at least part of the oxidant.

[0139] Fig. 3 illustrates a third exemplary embodiment of the present invention. Compared with the second exemplary embodiment, the water source 211 is preheated in a second oxygen-containing stream heat exchanger SHX2 to produce preheated water 219, which is then heated in the second heat exchanger 2HX2 to produce the steam stream 212 at the steam stream temperature. The oxygen-containing stream cooled by the first oxygencontaining stream heat exchanger SHX1 may then be further cooled by using via the second oxygen-containing stream heat exchanger SHX2 to atemperature of about 60°C, thus producing a cooled oxygen-containing stream 215.

[0140] Fig. 4 illustrates a fourth exemplary embodiment of the present invention. Compared with the third exemplary embodiment, the preheated water 219 is heated via a tertiary heat exchanger SHX3 to produce a saturated gaseous steam or superheated gaseous steam 223 using at least part of the heat of the hydrogen-containing stream, thereby cooling the at least part of hydrogencontaining stream and producing a cooled hydrogen-containing stream 224 at a temperature of about 50°C to about 180°C. The saturated gaseous steam or superheated gaseous steam is then heated via the second heat exchanger to produce the steam stream to be fed to the SOEC unit at a steam stream temperature. At least part of the cooled hydrogen-containing stream 224 is directly fed to the combustion chamber as part of the fuel.EXAMPLES

[0141] Example 1This Example corresponds to the first exemplary embodiment, without recycling of the hydrogen-containing stream.Fig. 5 shows the effect of oxygen concentration in the O2-enriched O2 / N2 mixture just before the inlet of a VSA unit. 21 vol% (rounded value for 20.95 vol%) represents the nominal oxygen concentration in air.VSA consumes about 0.36 kWh / Nm3oxygen approximately in standard conditions using air as inlet (O2, 21 vol%), whereas, if the oxygen concentration rises to about 30 vol% (about 9% enrichment) the energy consumption at VSA drops to 0.25 kWh / Nm3oxygen, which is a 30% decrease compared with the standard conditions.

[0142] Table 1

[0143] Accordingly, it is shown that integrating SOEC unit with an oxygen purificator, such as a VSA, purified oxygen at a concentration of about 80 vol% to about 99.8 vol% of oxygen could be produced with improved efficiency, with reduction of the power input to the oxygen purificator.

[0144] Example 2The following scenarios are considered: a) NG / Air combustion (Comparative Example 1) b) Energy equivalent base scenario using NG / O2 combustion (Comparative Example 2): air is fed to a VSA in order to produce a purified oxygen stream, which is used for the combustion; c) SOEC-VSA integration as in the second exemplary embodiment (Example 2).Example 2, as the third scenario, corresponds to the exemplary embodiments illustrated in the schematic diagrams of Figs. 2, 3 or 4, and shows a SOEC-VSA integration using flue gas heat as feedstock to enhance combustion efficiency and simultaneously produce the total or partial amount of hydrogen and / or oxygen used in the combustion process.

[0145] The SOEC unit may have a maximum size of 10 MW, which is capable of integrating the available heat described in the example (heat recovering from flue gas and SOEC downstream). In the third scenario, the integration of a 5 MW SOEC unit will serve as a comparison with the integration of a 10 MW SOEC unit.

[0146] Figs. 6a, 6b, 6c, and 6d show bar graphs, comparing the above scenarios using NG / Air, NG / O2 with VSA, SOEC-VSA (5MW) and SOEC-VSA (10MW) in terms of power consumption, natural gas consumption, and CO2 emission and O2 consumption.

[0147] More specifically, Fig. 6a shows the impact of oxygen concentration just before VSA (vol% of oxygen) on the VSA power input, in order to ensure the oxygen supply to the combustion chamber. As can be seen, with a 10 MW SOEC system, when a stream containing about 28 vol% of oxygen is provided to the VSA, up to about 30% the power consumption of a VSA unit can be reduced (30% less CO2 emissions compared with the standard case of NG / O2 combustion), compared with a typical VSA using air (21 vol% O2) as feedstock.

[0148] In addition, Figs. 6b and 6c show, respectively, the NG consumption at combustion and CO2 emissions for the three above scenarios. The reduction of NG consumption triggers a reduction of direct CO2 emissions up to about 59% compared with the NG / O2 scenario.

[0149] Finally, Fig. 6d shows the oxygen production from SOEC and make-up air needed to fill the combustion requirements. In the third scenario (scenario (c) above), even with a 10 MW SOEC unit, the use of make-up air is still required. However, compared with the second scenario (scenario (b) above), the total amount of oxygen and make-up air is reduced as a consequence of the enhancement of efficiency in the combustion process when a SOEC unit is integrated into the system. This reduction is even more pronounced in the case of a 10 MW SOEC unit.

[0150] In the third scenario (scenario (c) above), NG cannot be substituted by hydrogen completely, even with a 10 MW SOEC unit. A maximum of about 35% of the combustion heat can be supplied by the hydrogen-containing stream provided by a 5 MW SOEC unit, while a maximum of about 69% of the combustion heat can be supplied by the hydrogen-containing stream providedby a 10 MW SOEC unit. Access to free steam could enhance the scenario performance.

[0151] As in Example 1 , purified oxygen at a concentration of about 80 vol% to about 99.8 vol% of oxygen can be produced in Example 2.

[0152] Accordingly, the integration of an SOEC unit and an oxygen purificator into an industrial process requiring a combustion reaction has the following advantageous effects: valorizing waste heat and enhancing efficiency of the process by providing hydrogen and oxygen used for the combustion reaction, while improving the efficiency of the oxygen purificator.REFERENCE SIGNS LIST

[0153] 100: Exemplary system of the present invention101 : Water source102: Steam stream104: Sweep gas source105: Intermediate sweep gas106: Sweep gas107: SOEC unit108, 108a, 108b: Hydrogen-containing stream109: Oxygen-containing stream110: Cooled oxygen-containing stream111 : External source of air112: Mixture of the cooled oxygen-containing stream and air 113: Oxygen purificator114: Purified oxygen-containing stream 115: Separated sweep gas200: Exemplary system of the present invention201 : External source of CH4 for fuel202: Raw glass materials203: Flue gas204: Intermediate fluid205, 205a, 205b: Heated intermediate fluid206: Cooled flue gas207: SOEC unit208: Sweep gas source209: Intermediate sweep gas210: Sweep gas211 : External source of water212: Steam stream213, 213a, 213b: Hydrogen-containing stream214: Oxygen-containing stream215: Cooled oxygen-containing stream216: Oxygen purificator217: Purified oxygen-containing stream218a, 218b: Cold intermediate fluid to recycle219: Preheated water220: Melted glass materials221 : Fuel222: Oxygen-containing stream cooled by SHX1223: Saturated gaseous steam or superheated gaseous steam224: Cooled hydrogen-containing stream225: Separated sweep gasSHX1 : First oxygen-containing stream heat exchangerSHX2: Second oxygen-containing stream heat exchangerHX: Heat exchanger1 HX1 : Primary heat exchanger2HX1 : First heat exchanger2HX2: Second heat exchangerSHX3: Tertiary heat exchangerMC: Melting ChamberFN: FurnaceFG: Flue gas

Claims

CLAIMS1. A method for producing a purified oxygen-containing stream, the method comprising:- heating a Solid Oxide Electrolyzer Cells (SOEC) unit to a SOEC operating temperature;- providing a water source or a steam source at a water source or steam source temperature;- heating the water source or the steam source to produce a steam stream at a steam stream temperature;- providing a sweep gas at a sweep gas temperature;- feeding the steam stream and the sweep gas to the SOEC unit to produce an oxygen-containing stream and a hydrogen-containing stream;- cooling the oxygen-containing stream to a temperature in the range of about 20°C to about 100°C, preferably about 40°C to about 60°C, more preferably about 44°C to about 55°C, and even more preferably about 50°C; and- after the cooling step, purifying the oxygen-containing stream to produce the purified oxygen-containing stream.

2. The method of claim 1 , wherein cooling the oxygen-containing stream comprises transferring at least part of the heat of the oxygen-containing stream to a sweep gas source to produce an intermediate sweep gas at an intermediate sweep gas temperature lower than the sweep gas temperature, the method further comprising heating the intermediate sweep gas at the intermediate sweep gas temperature to produce the sweep gas at the sweep gas temperature.

3. The method of claim 1 or 2, wherein the sweep gas is air or oxygen-enriched air comprising higher than about 20.95 vol%, preferably at least about 23 vol%, more preferably at least about 24 vol%, even more preferably at least about 26 vol%, and still even more preferably at least about 28 vol% of oxygen.

4. The method of any one of claims 1 to 3, wherein the purified oxygencontaining stream comprises 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.

5. The method of any one of claims 1 to 4 further comprising:- after the cooling step and before the purifying step, mixing an external source of air with the cooled oxygen-containing stream.

6. The method according to any one of claims 1 to 5, 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.

7. A method of combusting a fuel, the method comprising:- producing a purified oxygen-containing stream according to the method of any one of claims 1 to 6; and- feeding the fuel and the purified oxygen-containing stream as part of an oxidant to a combustion chamber for combusting the fuel, wherein combusting the fuel with the oxidant generates flue gas.

8. The method of claim 7 further comprising:- using at least part of the hydrogen-containing stream as at least part of the fuel.

9. The method of claim 7 or 8, wherein the method is a continuous method, the method further comprising:- transferring at least part of the heat of the flue gas exiting the combustion chamber to an intermediate fluid, preferably air, thereby producing a heated intermediate fluid.

10. The method of claim 9, 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.11 . The method of claim 9 or 10, wherein cooling the oxygen-containing stream comprises transferring at least part of the heat of the oxygen-containing stream to a sweep gas source to produce an intermediate sweep gas at an intermediate sweep gas temperature lower than the sweep gas temperature, the method further comprising heating the intermediate sweep gas at the intermediate sweep gas temperature to produce the sweep gas at the sweep gas temperature, wherein heating the intermediate sweep gas at the intermediate sweep gas temperature to produce the sweep gas at the sweep gas temperature is performed by exchanging heat using at least part of the heat of the heated intermediate fluid.

12. The method of claim 11 , wherein cooling the oxygen-containing stream further comprises transferring to the water source or the steam source at least part of the heat of the oxygen-containing stream obtained after a heat transfer that produces the intermediate sweep gas, thereby producing preheated water or preheated steam at an intermediate water temperature or an intermediate steam temperature lower than a saturation temperature, and wherein heating the water source or the steam source to produce the steam stream at a steam stream temperature comprises heating the preheated water or the preheated steam to produce the steam stream at a steam stream temperature by exchanging heat using at least part of the heat of the heated intermediate fluid.

13. The method of any one of claims 9 to 11 , wherein heating the water source or the steam source to produce the steam stream at the steam stream temperature is performed by exchangingheat using at least part of the heat of the heated intermediate fluid.

14. A method of heating raw materials, preferably glass or cement materials, the method comprising:- combusting a fuel according to the method of any one of claims 7 to 13,- heating the raw materials with the heat generated by combusting the fuel with the oxidant.

15. A system for producing a purified oxygen-containing stream, the system comprising:- a Solid Oxide Electrolyzer Cells (SOEC) unit operable at 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 a sweep gas at a sweep gas temperature;- one or more oxygen-containing stream heat exchangers, and optionally a chiller unit, downstream of the SOEC unit to cool the oxygencontaining stream produced by the SOEC unit to a temperature in the range of about 20°C to about 100°C, preferably about 40°C to about 60°C, more preferably about 44°C to about 55°C, and even more preferably about 50°C, and- an oxygen purificator downstream of the one or more oxygencontaining stream heat exchangers, and optionally the chiller unit, configured to purify the oxygen-containing stream, thereby producing a purified oxygencontaining stream.

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