Process for heat treatment of input materials

Abstract

A process for thermally treating a non-gaseous input in a furnace (13), wherein carbon dioxide released by the input during said thermal treatment, a non-zero fraction (7) of a flue gas (6) containing said released carbon dioxide, is combined with hydrogen (3) and subjected to an rWGS reaction with said hydrogen (3), and then a reaction product (9) of the rWGS reaction is fed to the furnace (13) as fuel.

Description

Technical Field

[0001] The present invention relates to a process in which a non-gaseous input is heat-treated by combustion of fuel with an oxidant in a furnace where the non-gaseous input is heated.

Background Art

[0002] Hydrocarbon fuels have long been used for heating furnaces, and natural gas is often preferred due to its combination of low cost, high purity, and ease of control. However, the use of biogas is being increasingly promoted.

[0003] A disadvantage of hydrocarbon-containing fuels is that their combustion produces carbon dioxide.

[0004] When a reliable and stable power grid capable of generating sufficient electricity from renewable energy sources is available, replacing heating with combustion by electric heating can be just part of the way towards carbon removal in industrial furnaces.

[0005] Furthermore, not all processes for heat-treating inputs in a furnace are suitable for complete or partial replacement of heating by combustion by electric heating. Therefore, heating by combustion of fuel with an oxidant remains a mechanism in industrial furnaces.

[0006] The use of hydrogen as an alternative non-hydrocarbon fuel has also been proposed to reduce carbon dioxide emissions.

[0007] When hydrogen is produced using a renewable energy source, as in the case of electric heating, the replacement of hydrocarbon fuels with hydrogen can merely contribute to reducing the carbon footprint.

[0008] Furthermore, the characteristics of a hydrogen flame (e.g., flame volume, combustion gas composition, etc.) are quite different from those of a hydrocarbon flame. Therefore, a flame produced by hydrogen as a fuel is not suitable for all industrial heat treatment furnaces that have been conventionally burning hydrocarbon fuels.

Summary of the Invention

[0009] The object of the present invention is to provide an efficient method for heat-treating an input in a furnace, with or without reduced hydrocarbon combustion, thereby allowing the input to release carbon dioxide gas during the heat treatment. [Means for solving the problem]

[0010] According to the present invention, the reduction or elimination of hydrocarbon combustion is achieved by the effective use of carbon dioxide released by the input material during the heat treatment.

[0011] According to one embodiment, the present invention relates to a process in which an input material is heat-treated in a furnace where it is heated by the combustion of a fuel by an oxidizing agent.

[0012] In this context, the term "heat treatment" refers to a process in which the chemical and / or physical properties (other than mere temperature) of a non-gaseous input are altered under the effect of heat. Examples of such heat treatments include melting (e.g., glass melting), sintering, incineration, vitrification, and (re)crystallization (e.g., during metal reheating / annealing).

[0013] In the process of the present invention, a heat-treated non-gaseous input is introduced into a furnace. The furnace is heated by the combustion of a fuel with an oxidizer, and the fuel and oxidizer are supplied to the furnace at a controlled rate. A furnace atmosphere is generated in the furnace and consists of a gaseous mixture containing (a) combustion gases produced by the combustion of the fuel with an oxidizer, and (b) carbon dioxide released by the input during the heat treatment. The furnace atmosphere may also contain, and often contains, further components, such as substances other than CO2 released by the input during the heat treatment, incoming air, etc.

[0014] The heat-treated input is removed from the furnace, and the carbon dioxide-containing gaseous mixture is expelled from the furnace as flue gas.

[0015] According to the present invention, hydrogen is supplied to the process. The non-zero fraction of the flue gas combines with at least a portion of the supplied hydrogen, and the flue gas fraction contains at least 50% by volume and at most 100% by volume of CO2.

[0016] Next, the flue gas fraction is subjected to the rWGS reaction with hydrogen in a reverse water-gas shift (rWGS) reactor, and as a result, at least a portion of the CO2 in the flue gas fraction is converted to CO.

[0017] Next, the CO-containing reaction product of the rWGS reaction is supplied to the furnace as part or all of the fuel to be burned.

[0018] In this context, the term "gaseous mixture" refers to a gaseous medium containing multiple gaseous compounds. Furthermore, a "gaseous mixture" may also contain droplets or solid particles suspended in the gas phase, such as soot and dust.

[0019] The CO2 released by the input material may be due, for example, to the combustion of flammable materials present in the input material, and / or heat treatment, such as several other chemical reactions that occur in the input material during decarbonization.

[0020] As a result of the presence of rWGS reaction products in the fuel, the characteristics of the flame produced by combustion are more closely similar to those of a hydrocarbon flame than when only hydrogen is burned.

[0021] Furthermore, the CO2 released by the input material and removed from the furnace as flue gas is effectively utilized to improve heat treatment.

[0022] The rWGS reaction is known in the art and can be carried out as a catalyst or non-catalyst reaction. It is known, for example from U.S. Patent Application Publication A-2016 / 0083810, that the rWGS reaction can be used to convert CO2 to CO, after which a portion of the resulting CO is supplied to the blast furnace shaft as a reducing agent for the chemical reduction of metal ore contained therein, while the remaining portion of the resulting CO is directed to further processing.

[0023] The hydrogen supplied to the process is preferably hydrogen with a low or zero carbon footprint, such as so-called blue or green hydrogen. Green H2 is H2 produced with zero CO2 emissions, for example, through water electrolysis using renewable energy. Blue H2 exhibits emission intensity of up to 0.97 kg CO2 / kg H2 and can be produced, for example, by steam methane reforming with carbon capture. (van Cappellen, L., Croezen, H. & Rooijers, F. "Feasibility Study into Blue Hydrogen". CE Delft, 2018).

[0024] The CO2 content of the flue gas fraction that combines with hydrogen and is supplied to the rWGS is preferably as high as possible. The water content of the fraction is preferably as low as possible. In particular, the flue gas fraction preferably contains at least 80% by volume, preferably at least 90% by volume, and more preferably at least 98% by volume of CO2. Its humidity level is preferably 0 to 20% by volume of H2O, preferably at most 10% by volume of H2O.

[0025] The flue gas fraction sent to the rWGS reactor may simply be the portion of the removed flue gas and therefore have the same composition, in particular, the same CO2 and H2O content as the flue gas removed from the furnace. Preferably, the flue gas fraction sent to the rWGS has a higher CO2 content and / or a lower water content than the flue gas removed from the furnace, preferably both a higher CO2 content and a lower H2O content.

[0026] Such a flue gas fraction with concentrated CO2 is obtained by partially or completely removing one or more components other than CO2 from the flue gas. A particularly effective method for obtaining a flue gas fraction with concentrated CO2 is, for example, by removing water therefrom (dehumidification) by water condensation. To extract water from the flue gas by condensation, the flue gas is cooled to the water condensation temperature or below. According to a useful embodiment, the flue gas fraction with concentrated CO2 is reheated downstream of the water condensation step and upstream of the rWGS reaction, preferably using the residual heat recovered from the excluded flue gas.

[0027] In addition to water, other substances, such as dust particles, can be removed from the flue gas fraction during condensation. One or more further flue gas cleaning steps may be included in the process if necessary or appropriate.

[0028] The waste heat available on-site can be used to provide the energy (heat) required for the rWGS reaction.

[0029] In most processes for heat-treating non-gaseous inputs in a furnace, the flue gas is excluded from the furnace at a high temperature. For example, glass melting is usually realized in a furnace in which the flue gas is excluded at a temperature of 1300 °C to 1600 °C depending on the operating conditions and the requirements of the glass.

[0030] In such cases, the residual heat present in the excluded flue gas can be used in the rWGS reaction. In this context, the expression "residual heat" refers to the thermal energy that is excluded from the furnace via the excluded flue gas and thus has not been transferred to the inputs in the furnace.

[0031] When the excluded flue gas contains sufficient residual heat, the energy efficiency of the process can be improved by recovering heat from the excluded flue gas and supplying at least a part of the heat recovered from the excluded flue gas to the rWGS reaction.

[0032] The heat recovery process may be or may include an indirect heat recovery process, in which heat is first transferred from the flue gas to a solid or fluid heat recovery medium, and then the heat thus recovered is transferred from the heat recovery medium to the supplied hydrogen and / or the flue gas fraction and / or the combined flue gas fraction and hydrogen and / or the rWGS reactor itself, thus becoming available for the rWGS reaction.

[0033] In this way, heat can be recovered from the flue gas by heating the heat recovery fluid through heat exchange with the removed flue gas, and the heat thus recovered is • Heating the flue gas fraction by heat exchange with a heat recovery fluid heated upstream of the rWGS reaction, and / or • Heating the supplied hydrogen by heat exchange with a heat recovery fluid heated upstream of the rWGS reaction, and / or • Heating the combined flue gas fraction and hydrogen by heat exchange with the heated heat recovery fluid, and / or heating the reactor in which the rWGS reaction takes place. This can then be used to supply the rWGS reaction.

[0034] The heat recovery process is also, namely, The flue gas fraction is heated by heat exchange with the flue gas removed from the furnace upstream of the rWGS reaction, and / or • The supplied hydrogen is heated by heat exchange with the excluded flue gas upstream of the rWGS reaction, and / or • Heat the combined flue gas fraction and the reactor where the hydrogen and / or rWGS reaction occurs. It is heated by heat exchange with the removed flue gas. In this respect, it may be, or may include, a direct heat recovery process that does not involve an intermediate heat recovery medium.

[0035] Direct heat recovery is typically performed in a heat exchanger, where the fluid acting as the heat source and the fluid being heated are in thermal contact with each other across a heat exchange surface, while the heat exchange surface maintains physical separation (non-mixing) from each other.

[0036] Instead of, or in combination with, supplying heat recovered from the excluded flue gas to the rWGS reaction, the heat recovered from the excluded flue gas is also, • Preheating of oxidized material and / or • Fuel preheating and / or • Drying and / or preheating of non-gaseous inputs It can be used for this purpose.

[0037] In this context, the term “preheating” is used to describe the heating of all or part of the material to be introduced into the furnace, such as an oxidizer, fuel, or non-gaseous input, before the material in question is introduced into the furnace.

[0038] It is well known in the art to use residual heat from furnace flue gas to preheat oxidizers and / or fuels by direct or indirect heat exchange.

[0039] In the case of hydrocarbon fuels, the level (temperature) to which the fuel can be preheated is limited by phenomena such as fuel cracking.

[0040] Even if hydrogen is not used for cracking, the amount of residual thermal energy that can be recycled back into the furnace by hydrogen preheating is limited by its low mass flow rate.

[0041] In the process of the present invention, heating of the furnace using combustion of fuel by an oxidizer can be combined with a method of heating the furnace, such as electric heating.

[0042] Various methods for burning a fuel together with an oxidizer can be used in the context of the present invention. For example, the fuel may be burned in a furnace with one or more flames together with an oxidizer. The fuel may also be burned in a furnace with an oxidizer using stepwise or delayed combustion. According to certain embodiments, the fuel may be burned with an oxidizer by so-called flameless combustion, which is a form of highly stepwise combustion. These combustion methods are therefore known in the art.

[0043] According to one embodiment, all of the hydrogen supplied to the process is combined with the flue gas fraction and subjected to the rWGS reaction as described above.

[0044] According to an alternative embodiment, a first portion of the hydrogen supplied to the process is combined with the flue gas fraction and subjected to the rWGS reaction, while a further portion of the hydrogen supplied to the process is mixed with the reaction products of the rWGS reaction and / or separately injected into the furnace as further fuel.

[0045] In certain cases, it may also be useful to supply a gaseous hydrocarbon-containing fuel to the process and inject it into the furnace as additional fuel in addition to the rWGS reaction products. The gaseous hydrocarbon-containing fuel may be injected into the furnace mixed with and / or separately from the reaction products of the rWGS reaction. To keep the carbon footprint of the process as low as possible, the amount of hydrocarbon-containing fuel injected into the furnace should be kept as low as possible, and / or the hydrocarbon fuel injected into the furnace should preferably be obtained from a renewable source. Preferably, the energy supply to the process using hydrocarbon-containing fuel is less than or equal to the energy supply to the process using hydrogen. Typically, the energy supply using hydrocarbon-containing fuel is less than the energy supply using hydrogen (i.e., less than 100% of the energy supply using hydrogen), in particular less than 50% of the energy supply to the process by hydrogen, preferably less than 20%. However, it should be recognized that during startup or during interruptions in the heat treatment of inputs, i.e., when less CO2 is released by the inputs for the rWGS reaction, or when no CO2 is released, the use of higher levels of hydrocarbon-containing fuel may be required to heat the furnace.

[0046] By combining the heating of the furnace by the combustion of rWGS reaction products with other sources of thermal energy, such as electric heating or the combustion of further fuel (or both), the process flexibility is increased in that it becomes possible to meet the (varying) heat requirements of the furnace regardless of the level of CO2 emissions from the input materials in the furnace.

[0047] According to an advantageous embodiment, the process includes a step of automatically adjusting the amount of additional fuel injected into the furnace in addition to the reaction products of the rWGS reaction to meet the immediate heat requirements of the furnace. For the automatic adjustment of the amount of additional fuel injected into the furnace, a control unit is used that takes into account all sources of thermal energy supplied to the furnace, including, if present, electric heating, preheating of the rWGS reaction products, preheating of the additional fuel, preheating of the oxidizer and input heating. The automatically adjusted amount of additional fuel injected into the furnace and the amount injected of the rWGS reaction products thus together meet the immediate combustion heat requirements of the furnace.

[0048] The control unit can also be used to adjust the amount of oxidizer injected into the furnace, or more specifically, the amount of oxygen introduced into the furnace using the injected oxidizer. Depending on the type of furnace and heat treatment process (e.g., the properties of the input), the control unit may adjust the amount of oxidizer injected into the furnace as the amount of oxidizer stoichiometrically required for the complete combustion of the injected fuel. However, the adjusted amount of oxidizer injected into the furnace may also differ from the aforementioned stoichiometric amount. For example, the control unit may control the amount of oxidizer injected to maintain a reducing or oxidizing atmosphere in the furnace, in particular to avoid excessive oxidation or reduction of the input during heat treatment. The control unit may also consider the amount of oxygen entering the furnace as uncontrolled incoming air and subtract the incoming air oxygen from the adjusted amount of oxygen injected into the furnace with the oxidizer. The control unit may also consider any combustible materials that may be present in the input or released by the input during heat treatment and adapt to increase the amount of oxygen injected into the furnace to at least partially burn such combustible materials in the furnace. Methods and systems for controlling and adjusting the amount of oxidizer injected into the furnace are known in the art and may include methods or systems for detecting the presence and / or level of flammable material in the furnace flue gas.

[0049] Furthermore, when thermal energy is again supplied to the furnace by electric heating, a control unit can be used to adjust the amount of electric heating and the amount of thermal energy supplied thereby.

[0050] The oxidizer used may be air. It is often preferable to use an oxidizer with a higher oxygen content than that of air. For example, the oxidizer usefully has an oxygen content of 70% to 100% by volume, preferably at least 85% by volume, and more preferably at least 95% by volume. By reducing the amount of inert ballast gas in the high-oxygen oxidizer, the heating efficiency of combustion can be improved compared to 78% by volume of N2 in air.

[0051] As previously shown, according to the present invention, the heat treatment is improved by using CO2 released by the input during the heat treatment. One particular effect of supplying hydrogen to the rWGS reaction together with the CO2 released by the input is that a flame more closely resembling a hydrocarbon flame is obtained. In addition to, or instead of, the CO2 released by the input during the heat treatment, CO2 from an external source may also be used for the rWGS reaction. The use of external CO2 is useful, for example, to allow hydrogen to be supplied to rWGS during startup, when the heat treatment of the input in the furnace is interrupted, or when the input that releases little or no CO2 during the heat treatment is being processed in the furnace (e.g., cullet in a glass melting furnace). In such cases, CO2 from other sources may also be used in the process. In order to keep the carbon footprint as low as possible, in this case, it is preferable to use CO2 available from other on-site sources. As a result, the method of the present invention contributes to reducing the carbon footprint of the site.

[0052] As previously shown, the present invention is applicable to a wide range of heat treatment processes, including processes other than those for the chemical reduction of metal ores.

[0053] The present invention is of particular interest to glass melting processes and furnaces.

[0054] Glassmaking involves the process of producing molten glass by melting a solid glass-forming material. For this purpose, the solid glass-forming material is introduced into a furnace, where it is heated and melted. This melting process is energy-intensive.

[0055] Both combustion and electricity have been used, separately and in combination, to generate the necessary heat.

[0056] In industrial electric glass melting furnaces, melting energy is supplied by electrodes embedded in the glass-forming material (Joule heating), and as a result, all the generated heat is transferred to the glass-forming material surrounding the electrodes.

[0057] Electric glass melting furnaces (EMs), also known as 100% electric industrial glass melting furnaces, have relatively low capital costs but also short lifespans (2-7 years) and high energy costs. The economic sustainability of electric furnaces is closely related to the cost of electricity compared to the cost of hydrocarbon fuels.

[0058] As a result, EM is typically used for specialty glass, particularly glass with significant volatile components, such as fluoride opal glass, borosilicate glass, and red crystal. EM typically has a glass production capacity ranging from 10 to 100 tpd per day. There are only about 50 EM units worldwide with a production capacity of 100 to 250 tpd. EM accounts for less than 5% of the world's glass furnaces.

[0059] Furthermore, even the use of completely carbon-free electricity cannot completely decarbonize the glass melting process. In fact, in almost all cases, carbon dioxide is released by the inputs during melting and / or purification. In practice, the production of 1 kg of glass produces, on average, approximately 0.15 kg of CO2 from the dissociation of carbonate raw materials (e.g., CaCO3 and dolomite) in the solid glass-forming material. The amount of CO2 released is directly related to the type of glass and the use of recycled glass, also known as cullet. A possible exception is the production of glass based on completely clean recycled glass / cullet, but these processes only constitute a very small part of the glass melting industry.

[0060] The CO2 released by the input of glass-forming materials not only contributes to the carbon dioxide emissions of the glass production process, but also constitutes a source of energy loss, as thermal energy is consumed during the generation of CO2 and during the heating of the resulting CO2 to the furnace atmosphere temperature, after which the heated CO2 is removed from the furnace as part of the furnace flue gas. In this way, this CO2 absorbs some of the heat supplied to the furnace and acts as ballast, removing further heat from the furnace by an increased amount of furnace flue gas.

[0061] Most glass melting furnaces rely entirely or primarily on the combustion of hydrocarbon fuels for their energy requirements, either alone or in combination with electric heating. Natural gas has long been the preferred hydrocarbon fuel. Natural gas furnaces have a long lifespan, averaging over 12 years, and sometimes up to 20 years.

[0062] Novel technologies that enable the replacement of air with oxygen-concentrated air or oxygen have been developed to reduce NOx emissions and / or improve the energy efficiency of combustion-heated glass melting furnaces.

[0063] As previously shown, replacing (part of) the energy requirements of a glass melting furnace with electric heating or hydrogen combustion can be just one factor in reducing overall CO2 emissions when the electricity or hydrogen is generated using renewable resources.

[0064] Furthermore, hydrogen flames are less abundant, and therefore achieve a smaller coverage (in terms of surface area) of the glass-forming material. This problem becomes more complex when oxygen is used as the oxidizer for combustion.

[0065] Furthermore, hydrogen flames have a higher H2O content than the corresponding hydrocarbon flames. High H2O partial pressure in the furnace atmosphere has been associated with the formation of an insulating foam layer on the molten glass.

[0066] In the process of the present invention, when the furnace is a glass melting furnace, the solid glass-forming material to be melted is introduced into the furnace as a heat-treated input, and the molten glass is removed from the furnace as a heat-treated input. When the glass-melting material is simply subjected to melting in the process / furnace, the heat treatment to which the input is subjected consists of melting. When the glass-melting material is subjected to both melting and refining in the process / furnace, the heat treatment to which the input is subjected consists of a combination of melting and refining (in this order). Carbon dioxide is released into the furnace atmosphere by the glass-forming material during its heat treatment, as discussed above.

[0067] As a result of the presence of rWGS reaction products in the fuel, a larger and brighter flame is obtained on the input compared to when hydrogen is supplied to the reactor as part or all of the fuel without the rWGS reaction by the flue gas fraction.

[0068] This results in more effective heating of the glass-forming material.

[0069] Furthermore, the partial pressure of H2O in the reactor atmosphere is lower compared to the case where hydrogen is supplied to the reactor as part or all of the fuel without the rWGS reaction by the flue gas fraction.

[0070] Furthermore, as already mentioned above, some of the CO2 released by the inputs and removed from the furnace as flue gas is recycled and used to improve the energy efficiency of the furnace.

[0071] In the case of a glass melting furnace, the flue gas is removed at a high temperature (e.g., 1300°C to 1600°C). Thus, the flue gas contains a high level of residual heat, which can be supplied at least partially to the rWGS reaction.

[0072] Consequently, heat recovery from flue gas using any of the previously described methods is particularly useful for the glass melting process.

[0073] According to certain embodiments, heating of a furnace using the combustion of a fuel with an oxidizer is combined with electric heating of the furnace. In particular, the furnace can be heated simultaneously by both the above combustion of a fuel with an oxidizer and by electrodes embedded in a glass-forming material.

[0074] One such process involves using electric heating to boost the melting process. In this context, "electric boosting" refers to a process in which 5-50%, preferably 20-50%, of the energy supplied to the furnace is supplied to the furnace by electric heating using electrodes.

[0075] According to an alternative embodiment, the process is a hybrid melting process. In the hybrid process, 30-95%, preferably 50-95%, of the energy supplied to the furnace is supplied by electric heating using electrodes, and the remainder is supplied by combustion. Thus, the furnace (30-50% of the energy supplied to the furnace is supplied by electric heating using electrodes, while the remainder is supplied by combustion) can be considered as a boosted furnace or a hybrid furnace.

[0076] In such a process in which the furnace is heated using a combination of combustion and electric heating, those skilled in the art will recognize that, as is also customary for 100% electric melting furnaces, the furnace may occasionally be heated only by combustion, such as during startup.

[0077] The use of electric heating to complement the heat generated by combustion increases the flexibility of the glass melting furnace, maintaining the desired quality of the molten glass while making it easier to adapt the furnace heating to changes in the composition of the glass-forming input and / or changes in the glass formation rate (pulling rate). Thus, by combining heating by combustion and electric heating, the process can be easily used and adjusted for melting glass-forming materials with or without recycled glass, and for melting different types of glass.

[0078] A further consequence of combining combustion heating and electric heating in the process according to the present invention is that less combustion gas is produced for the same amount of heat generated. As a result, the concentration of CO2 released by the input during heat treatment is higher than in the case of a furnace heated by combustion alone, and therefore it is easier to obtain a high-CO2 flue gas fraction that combines with H2 and is sent to the rWGS reactor according to the present invention.

[0079] Similar advantageous effects can be obtained when the need to supply heat to the furnace using the combustion of fuel by the oxidizer is reduced by preheating the oxidizer and / or the fuel, and / or drying and / or preheating the glass-forming material.

[0080] The flame coverage of the glass-forming material can be improved by injecting fuel and oxidizer into the furnace at multiple locations to generate multiple flames.

[0081] A so-called flat flame, where the width of the flame parallel to the material being fed is smaller than the height of the flame perpendicular to the material being fed, can also improve the flame coverage of the material being fed.

[0082] Stepped combustion or delayed combustion are further means of achieving improved flame coverage of the input material.

[0083] When the only fuel supplied to the process is hydrogen, as opposed to the carbon dioxide produced by the process, the only carbon dioxide produced by the process is the carbon dioxide initially released by the glass-forming material. This is also true for the carbon dioxide produced by the combustion of the rWGS reaction product obtained by subjecting the flue gas fraction to the rWGS reaction with hydrogen.

[0084] In the glass melting process according to the present invention, a hydrocarbon-containing fuel, such as natural gas or biogas, may also be supplied to the process in addition to the supplied hydrogen. The further hydrocarbon fuel may be injected into the furnace mixed with and / or separately from the rWGS reaction product. In this case, the process produces not only the carbon dioxide initially released by the glass-forming material in the furnace, but also the carbon dioxide initially produced by the combustion of the further fuel.

[0085] When hydrocarbon fuels are supplied to the process, it is preferable to use hydrocarbon-containing fuels produced from renewable sources as additional fuel to keep the carbon footprint of the glass melting process as low as possible.

[0086] Along with this, the oxidizer into which the fuel is burned can be air, but as previously discussed, an oxidizer having a higher oxygen content than air is generally preferred.

[0087] The reduced or even absent presence of ballast gas nitrogen in such oxygen-rich oxidizers enhances the efficiency of the heating process. A further advantage is that the reduced or absent amount of ballast gas again removes flue gas with a higher CO2 concentration from the furnace, thereby making it easier to extract the CO2-rich fraction supplied to the rWGS reaction along with the supplied hydrogen from the removed flue gas.

[0088] A disadvantage typically encountered in combustion with oxygen-rich oxidizers is that, compared to combustion with air, it produces a flame with a smaller volume, i.e., one that covers a smaller surface area of ​​the input material. This is at least partially compensated for by the present invention through the injection of the reaction products of the rWGS reaction as part of the fuel to be burned in the furnace.

[0089] The present invention is illustrated by reference to a diagram showing a schematic flowchart of a specific embodiment of the process according to the present invention applied to a glass melting furnace. [Brief explanation of the drawing]

[0090] [Figure 1] Figure 1 is a schematic flowchart of a specific embodiment of the process according to the present invention applied to a glass melting furnace. [Modes for carrying out the invention]

[0091] Furnace 13 is a glass melting furnace into which solid glass-forming material is continuously introduced at the supply end and molten glass is continuously removed at the opposite end of the furnace (not shown). Furnace 13 is heated by the combustion of fuel by oxidizers on the input glass-forming material, thereby introducing combustion gases into the furnace atmosphere.

[0092] Furthermore, the power 10 can be supplied to electrodes (not shown) in the furnace 13 to boost the heat supply to the furnace.

[0093] As the glass-forming material is heated and melts, it releases a series of compounds, including a considerable amount of CO2, into the furnace atmosphere.

[0094] Since the furnace is not airtight, there is an unavoidable intrusion of air into the furnace 11, and this intrusion of air also forms part of the furnace atmosphere.

[0095] The resulting gas mixture is continuously removed from the furnace as flue gas flow 6 at a temperature of approximately 1450°C. The CO2 content of the removed flue gas flow 6 is approximately 42% by volume.

[0096] The residual heat is recovered from the flue gas flow 6 that has been removed in the heat exchanger 6a, thereby lowering the temperature of the flue gas to approximately 512°C, which is considerably above the condensation temperature of water vapor present in the flue gas flow 6.

[0097] The cooled flue gas flow 6b is divided into two parts: a recirculated flue gas flow 12 and a stale flow 8 (which is removed from the process). In particular, the need arises to remove the stale flow 8 from the process because new CO2 is continuously released by the inputs in the furnace 13 and removed from there as part of the flue gas. Without the stale flow 8, the amount of CO2 in the process continues to accumulate. Such purging is also required to remove nitrogen introduced by the incoming air from the process. The stale flow 8 may be subjected to one or more cleaning steps, for example, before being released into the atmosphere. However, where possible, the stale flow 8 is subjected to CCUS as a further measure to reduce the carbon footprint of the glass melting process.

[0098] In the cooler 15, the recirculating flow 12 is further cooled, causing the water to condense, thereby increasing the CO2 content in the gas phase. The condensed water is removed as flow 5.

[0099] The recirculated flow 7, which has been at least partially dehumidified, has a CO2 content of approximately 70% by volume and is sent to the rWGS reactor 14.

[0100] In addition to the recirculating flow 7, the hydrogen flow 3 is also sent to the rWGS reactor 14, where the CO2 from the recirculating flow 7 reacts with the hydrogen from flow 3 as follows: CO2 + H2 ⇔ CO + H2O.

[0101] The resulting rWGS reaction product stream 9, containing both CO and H2, is injected into the furnace 13 as fuel, producing a flame coverage of the glass-forming material in the furnace 13, which is more closely similar to the flame coverage obtained using the combustion of hydrocarbon fuel than a hydrogen flame, but without the further CO2 emissions of hydrocarbon combustion.

[0102] An oxygen-rich oxidizer, more specifically, a stream of industrial-grade oxygen 2, is preheated in a heat exchanger 2a, and then the preheated oxidizer stream 2b is sent to a furnace 13 and injected into it as a combustion oxidizer for the combustion of fuel.

[0103] Optionally, in addition to the recirculating flow 7, CO2 from an external source may also be supplied to the rWGS reactor 14. In the illustrated embodiment, an additional CO2-containing flow 4 is mixed with the hydrogen flow 3 in a static mixer 16, and the mixed H2+CO2 flow is supplied to the rWGS reactor 14, where it combines with the recirculating flow 7 and is subjected to the rWGS reaction.

[0104] Optionally, additional fuel may be supplied to the furnace 13 in addition to the rWGS reaction product flow 9. In the illustrated embodiment, the additional fuel flow 1 is preheated in the heat exchanger 1a, and the preheated additional fuel flow 1b is sent to the furnace 13 and injected into it together with a portion of the preheated oxidizer flow 2b to be burned in the furnace.

[0105] The additional fuel flows 1 and 1b may preferably be hydrocarbon-containing fuel flows produced from a renewable source. The additional fuel flows 1 and 1b may also be hydrogen flows that are injected into the reactor 13 without being subjected to the rWGS reaction first.

[0106] Reference numeral 17 indicates a heat recovery assembly for the illustrated process. Using the heat recovery assembly, residual heat present in the removed flue gas flow 6 is recovered using a heat exchanger 6a and used (a) as a heat source for the rWGS reaction in reactor 14, (b) as a heat source for preheating the oxidizer flow 2 in heat exchanger 2a, and (c) as a heat source for preheating the additional fuel flow 1 in heat exchanger 1a when additional fuel is supplied to the furnace.

[0107] In the simplified layout diagram of the figure, the different steps of the heat recovery process are shown separately for the sake of clarity. However, as previously discussed, it should be recognized that the heat recovery step of heat exchanger 6a is necessarily related to the heat supply step to the rWGS reaction in reactor 14, and the preheating step of heat exchangers 1a and 2a, which depends on the heat recovered in the heat recovery step. Furthermore, any one of the steps may consist of multiple substeps. For example, the heat recovery step of heat exchanger 6a may include a high-temperature heat recovery substep, followed by a low-temperature heat recovery substep. However, as also discussed above in this specification, those skilled in the art will recognize that the heat recovered between different heat recovery substeps may be used in different heat supply steps. The step of supplying the recovered heat to the rWGS reaction in rWGS reactor 14 may consist, for example, of supplying heat to reactor 14, or may include a substep of heating the dehumidified recirculation flow 7 upstream of rWGS reactor 14.

[0108] The type of embodiment illustrated in [Figure 1] is not limited to a glass forming process, but can be applied to other methods for heat-treating input materials, thereby recognizing that the input material releases CO2 during the heat treatment, and the hot flue gas containing the released CO2 is removed from the furnace in which the heat treatment takes place.

[0109] By using the process according to the present invention, CO2 released by the glass-forming material (which typically contributes to energy loss in the glass melting process) is at least partially recirculated and reused, improving the heating of the input material in the furnace. Furthermore, the present invention also enables the optimized use of residual heat present in the furnace flue gas.

Claims

1. - The heat-treated non-gaseous input is introduced into the furnace (13), - The furnace (13) is heated by the combustion of fuel (1, 1b, 9) with oxidizer (2, 2b), and the fuel (1, 1b, 9) and oxidizer (2, 2b) are supplied to the furnace (13) at a controlled supply rate. - An atmosphere is generated in the furnace (13), and the atmosphere consists of (a) combustion gases produced by the combustion of the fuel (1, 9) by the oxidizer (2, 2b), and (b) a gaseous mixture containing carbon dioxide released by the input during the heat treatment. - The heat-treated input is removed from the furnace (13), - The gaseous mixture is removed from the furnace (13) as flue gas (6). It is a process, - Hydrogen (3) is supplied to the process and contains at least 50% by volume and a maximum of 100% by volume of CO ２ The non-zero fraction (7) of the flue gas (6) containing CO combines with at least a portion of the supplied hydrogen (3) and is subjected to an rWGS reaction with the hydrogen (3) in the rWGS reactor (14), thereby reducing the CO in the fraction (7). ２ At least a portion of it is converted to CO, - The reaction product (9) of the rWGS reaction is supplied to the furnace (13) as part or all of the fuel (1, 1b, 9) to be burned. The aforementioned process is a glass melting process, - The solid glass-forming material to be melted is introduced into the furnace (13) as the heat-treated non-gaseous input, - Carbon dioxide is released into the furnace (13) atmosphere by the glass-forming material during the heat treatment. - The molten glass is removed from the furnace (13) as the heat-treated input. A process characterized by the following features.

2. The fraction (7) of the flue gas (6) is - At least 80% by volume, preferably at least 90% by volume, more preferably at least Both contain 98% CO ２ and / or ・H 0-20% by volume ２ O, preferably, at most 10% by volume of H ２ O The process according to claim 1, including the process described in claim 1.

3. The process according to claim 1 or 2, wherein the fraction (7) of the flue gas (6) is preferably a dehumidified flue gas fraction obtained by removing water therefrom by condensation.

4. The process according to any one of claims 1 to 3, wherein heat is recovered from the excluded flue gas (6) and supplied to the rWGS reaction.

5. The heat recovered from the excluded flue gas (6) is supplied to the rWGS reaction by using the recovered heat, heating the fraction (7) of the flue gas (6) upstream of the rWGS reactor (14), and / or heating at least a portion of the supplied hydrogen (3) upstream of the rWGS reactor (14), and / or heating the combined fraction (7) of the flue gas (6) and at least a portion of the supplied hydrogen (3) upstream of the rWGS reactor (14), and / or heating the rWGS reactor ( The process according to claim 4, comprising: heating 14); preferably heating the fraction (7) of the flue gas (6) upstream of the rWGS reactor (14) and / or heating the combined fraction (7) of the flue gas (6) and at least a portion of the supplied hydrogen (3) upstream of the rWGS reactor (14) and / or heating the rWGS reactor (14), more preferably heating the fraction (7) of the flue gas (6) upstream of the rWGS reactor (14) and / or heating the rWGS reactor (14).

6. The heat is recovered from the removed flue gas (6), Preheating of the oxidized material and / or Fuel preheating and / or Drying and / or preheating of the heat-treated input. A process according to any one of claims 1 to 5, used for the purpose of

7. The process according to any one of claims 1 to 6, wherein a further portion (1, 1b) of the hydrogen supplied to the process is mixed with and / or separately injected into the furnace (13) as further fuel.

8. The process according to any one of claims 1 to 7, wherein a gaseous hydrocarbon-containing fuel (1, 1b) is supplied to the process and mixed with the reaction product (9) of the rWGS reaction and / or separately therefrom, and injected into the furnace (13) as further fuel, wherein the gaseous hydrocarbon-containing fuel (1, 1b) is preferably obtained from a renewable source.

9. The process according to claim 7 or 8, wherein the amount of further fuel injected into the furnace (13) is automatically adjusted so that the immediate combustion heat requirement of the furnace (13) is met by the combustion of the reaction product (9) of the rWGS reaction together with the combustion of the further injected fuel (1, 1b).

10. The process according to any one of claims 1 to 9, wherein the oxidized product (2, 2b) has an oxygen content of 70% to 100% by volume, preferably at least 85% by volume, and more preferably at least 95% by volume.

11. The fuel (1, 9) is burned by multiple flames and / or by stepwise combustion, the oxidizer (2, The process according to any one of claims 1 to 10, wherein the process is carried out together with 2b).

12. The furnace (13) a) Combustion of fuel (1, 9) by oxidizer (2, 2b) and b) Electrodes embedded in the glass forming material The process according to any one of claims 1 to 11, wherein heating is performed simultaneously using [a specific method].

13. The process according to claim 12, wherein 5 to 50%, preferably 20 to 50%, of the energy supplied to the furnace (13) is supplied to the furnace (13) using the electrodes.

14. The process according to claim 12, wherein 30 to 95%, preferably 50 to 95%, of the energy supplied to the furnace (13) is supplied to the furnace (13) using the electrodes.

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