RESTORATION OF METAL OXIDE CONTAINING MATERIAL USING AMMONIA NH3 AND CARBON GAS
Patent Information
- Authority / Receiving Office
- RU · RU
- Patent Type
- Applications
- Current Assignee / Owner
- PRIMETALS TECH AUSTRIA GMBH
- Filing Date
- 2024-10-29
- Publication Date
- 2026-07-02
AI Technical Summary
Existing methods for reducing metal oxide-containing materials, such as iron oxide, using reducing gases like carbon-containing gases result in high CO2 emissions, and the use of hydrogen as a reducing agent is hindered by its difficult storage and transport. Additionally, ammonia splitting reactions are endothermic and require careful thermodynamic and kinetic control.
A process involving the use of a mixture of ammonia (NH3) and carbon-containing gases to produce a reduction gas, where ammonia is split at temperatures between 350°C and 650°C to create a gap mixture rich in nitrogen and hydrogen. This split gas mixture is then exposed to reforming conditions at temperatures between 700°C and 1150°C to produce a reforming gas that contributes to the reduction process.
This approach reduces CO2 emissions by utilizing ammonia as a reducing agent, which is more easily stored and transported than hydrogen. The process effectively maintains the necessary thermodynamic and kinetic conditions for ammonia splitting and reforming, avoiding adverse interactions and improving the efficiency of metal oxide reduction.
Abstract
Description
[0001] Description
[0002] Reduction of metal oxide-containing material based on ammonia NH3 and carbon-containing gas
[0003] field of technology
[0004] The application relates to a method and device for the reduction of metal oxide-containing material, wherein a reducing gas obtained using ammonia NH3 and carbon-containing gas is used.
[0005] State of the art
[0006] It is known to reduce materials containing metal oxides, such as iron oxides, such as ores, using reducing gas. This is done, for example, by direct reduction with reducing gas in a reduction unit, such as a reduction shaft. In the blast furnace process, carbon monoxide (CO), for example, also acts as a reducing gas in the blast furnace reduction unit. In conventional processes currently used on a large scale, the reducing gas is predominantly based on carbon-containing gases, such as natural gas or coke oven gas. Therefore, large quantities of carbon dioxide (CO2) are produced, which is undesirable for environmental reasons, among other things.
[0007] To reduce CO2 emissions during the reduction of metal oxide-containing materials, it is known to use hydrogen (H2) as a reducing gas. Hydrogen can be used as the sole reducing gas or in combination with other gases, such as natural gas-based reducing gases. The higher the proportion of CO2-neutral hydrogen (H2) in the reducing gas, the less CO2 is emitted.
[0008] However, storage of hydrogen H2 and transport from the place of its production to consumers is problematic and involves great effort due to its physical properties.
[0009] To reduce CO2 emissions during the reduction of metal oxide-containing materials, it is also known to use ammonia (NH3) as a reducing agent. Ammonia offers significant advantages over hydrogen (H2) in terms of storage and transport. Ammonia can be split into nitrogen and hydrogen.
[0010] 2 NH3 -> N2 + 3 H2
[0011] Hydrogen H2 can react as a reducing agent with metal oxides, for example iron oxides:
[0012] Ammonia can also act as a reducing agent itself:
[0013] 9 Fe2O3+ 2 NH3-> 6 Fe3O4+ N2+ 3 H2O
[0014] 3 Fe3O4+ 2 NH3-> 9 FeO + N2+ 3 H2O
[0015] 3 FeO + 2 NH3-> 3 Fe + N2+ 3 H2O
[0016] In principle, reducing gas obtained using ammonia NH3 can be used to reduce metal oxide-containing material. Such a reducing gas can be, for example, ammonia NH3, or a mixture of ammonia NH3 with one or more other gases—whereby preferably one or more can have a reducing effect on metal oxide-containing material—which would be the case, for example, with a mixture of ammonia and its decomposition products hydrogen H2 and nitrogen N2, although, of course, other gases could also be included in the mixture.However, the reducing gas obtained using ammonia NH3 can also be a reducing gas that does not contain ammonia NH3, but contains the fission product hydrogen H2- obtained from a fission, alone or together with the fission product nitrogen N2-, optionally in a mixture with one or more other gases - preferably one or more of which can have a reducing effect on metal oxide-containing material.
[0017] Such reduction reactions for the production of metallic iron (Fe) with hydrogen (H2) and ammonia (NH3), as well as the splitting of ammonia into nitrogen (N2) and hydrogen (H2), are endothermic. This gives rise to problems regarding maintaining the thermodynamic and kinetic conditions necessary for industrial implementation of the reduction. A balance between the effort to reduce carbon dioxide emissions through increased use of ammonia (NH3) and the problems associated with ammonia use can be achieved by combining ammonia and carbon-containing gas.
[0018] Summary of the invention
[0019] Technical task
[0020] It is the object of the present invention to present a possibility for the joint use of ammonia and carbon-containing gas in the reduction of metal oxide-containing material.
[0021] Technical solution
[0022] The task is solved by a
[0023] A process for the reduction of metal oxide-containing material, wherein a reducing gas obtained using ammonia NH3 and using carbon-containing gas is used by introducing it into a reduction unit, characterized in that during the production of the reducing gas, a mixture comprising ammonia and carbon-containing gas is prepared, and at least a portion of the mixture is first exposed to ammonia-splitting conditions at a temperature in a range with a lower limit of 350°C, preferably 450°C, and an upper limit of 650°C, preferably 550°C, whereby a cracked gas mixture is formed, and then at least a portion of the cracked gas mixture is exposed to reforming conditions for reforming carbon-containing gas at a temperature in a range with a lower limit of 700°C and an upper limit of 1150°C, preferably 1000°C,and the reforming gas obtained after passing through the reforming conditions contributes to the reducing gas.
[0024] The metal oxide-containing material is preferably iron oxide-containing material. The reduction process is, for example, a direct reduction process.
[0025] The reducing gas is obtained using ammonia NH3, ammonia contributes to the reducing gas.
[0026] The reducing gas is, for example, a mixture of ammonia NH3 with one or more other gases. However, the reducing gas obtained using ammonia NH3 can also be a reducing gas that does not contain ammonia NH3, but contains the fission product hydrogen H2 obtained from a fission reaction—alone or together with the fission product nitrogen N2—mixed with one or more other gases.
[0027] The reducing gas can therefore contain ammonia; it consists partly of ammonia and additionally of other components.
[0028] As further components of the reducing gas, components that have a reducing effect on the metal oxide-containing material are preferred; such components can be, for example, hydrocarbon-containing gases, carbon-containing gases, hydrogen-containing gases, or hydrogen.
[0029] According to the invention, reducing gas is obtained using ammonia by splitting ammonia and contributing the resulting split gas mixture comprising nitrogen and hydrogen and optionally ammonia - optionally after enrichment of hydrogen or depletion of nitrogen - to the reducing gas.
[0030] Ammonia contributes to the reducing gas, which is in addition to the contribution made by the carbon-containing gas. Ammonia provides other components of the reducing gas, in addition to the components contributed by the use of carbon-containing gas.
[0031] The decomposition of ammonia NH3 occurs at a temperature within a range with a lower limit and an upper limit under ammonia-decomposing conditions. The lower limit of the range can be 350°C, preferably 450°C. The upper limit of the range can be 650°C, preferably 550°C.
[0032] This produces a cracked gas mixture comprising nitrogen and hydrogen—and optionally ammonia—from the mixture of ammonia and carbon-containing gas. The cracked gas mixture also contains ammonia if not all of the ammonia in the mixture is converted under the ammonia-splitting conditions, but only a portion of the ammonia in the mixture. The unreacted remainder of the ammonia from the mixture is then present in the cracked gas mixture as ammonia. An ammonia content of up to 10 vol%, preferably up to 8 vol%, particularly preferably up to 6 vol% in the cracked gas mixture is acceptable.
[0033] To achieve ammonia-splitting conditions, catalysts are used that catalyze ammonia splitting in this temperature range.
[0034] In principle, ammonia of any color is suitable. "Color" refers to the coloring in connection with the underlying production method. The color of the ammonia is often linked to the color of the hydrogen used in production. The ammonia can be green, for example, if it was produced using green hydrogen; it can be blue, for example, if it was produced using hydrogen obtained by sequestering carbon dioxide (CO2). Ammonia can also be produced using turquoise hydrogen, for example, if the hydrogen is produced by capturing carbon dioxide (C); it can be produced using pink hydrogen, for example, if the hydrogen is produced using nuclear power.A mixture of one or more of these “colors” of ammonia, or a mixture of colors of the hydrogen underlying ammonia, is also possible.
[0035] The reducing gas is obtained using carbon-containing gas. The carbon-containing gas can be a pure gas, such as pure methane, or a carbon-containing mixture of several gases, such as natural gas or coke oven gas. The carbon in the carbon-containing gas can be present, for example, as a hydrocarbon, such as methane CH4, ethane C2H6, propane C3H8, butane C4H10, or as carbon monoxide CO, or as carbon dioxide CO2.
[0036] A carbon-containing gas used can, for example, be natural gas or top gas discharged from the reduction unit - possibly after processing.
[0037] The carbon-containing gas contributes to the reducing gas, this contribution being in addition to the contribution to the reducing gas made by ammonia.
[0038] The carbon-containing gas provides—in addition to the components contributed by the use of ammonia—further components of the reducing gas. As such, further components of the reducing gas are preferred, components that have a reducing effect on the metal oxide-containing material; these can be, for example, hydrocarbon-containing gases, carbon-containing gases, hydrogen-containing gases, or hydrogen. According to the invention, the use of carbon-containing gas occurs at least with reforming of carbon-containing gas. At least a portion of the cracked gas mixture is subjected to reforming conditions at a temperature in a range with a lower limit of 700°C and an upper limit of 1150°C, preferably 1000°C. To achieve reforming conditions, catalysts are used that catalyze reforming in this temperature range—called reforming catalysts.Reforming conditions are the conditions under which the reforming of carbon-containing gas takes place. Reforming is the reforming of carbon-containing gas. Reforming conditions exist in a reforming device such that it is suitable for reforming carbon-containing gas.
[0039] The reforming takes place, for example, as steam reforming and / or CO2 reforming according to
[0040] CH4+H2O— >CO+3H2
[0041] CH4+CO2— >2CO+2H2.
[0042] This is illustrated using methane CH4 as an example; for higher hydrocarbon compounds, the reforming process is analogous.
[0043] According to the invention, a mixture comprising ammonia and a carbon-containing gas is prepared during the production of the reducing gas. The mixture can be prepared, for example, by combining ammonia with one or more carbon-containing gases; for example, by combining ammonia with top gas—optionally after processing the top gas—and / or natural gas. If several carbon-containing gases are combined, these can be mixed together with the ammonia, or, for example, a first carbon-containing gas can first be mixed with ammonia, and then a second carbon-containing gas can be added to the resulting mixture to obtain the mixture that serves as the basis for the cracked gas mixture.For example, top gas, which is a carbon-containing gas and may be upgraded, can first be mixed with ammonia and then natural gas added before being subjected to ammonia-splitting conditions.
[0044] A portion or the entire mixture is first exposed to ammonia-splitting conditions at a temperature in a range with a lower limit of 350°C, preferably 450°C, and an upper limit of 650°C, preferably 550°C, to form a cracked gas mixture, and then at least a portion of the cracked gas mixture is exposed to reforming conditions at a temperature in a range with a lower limit of 700°C and an upper limit of 1150°C, preferably 1000°C.
[0045] With regard to the mixture comprising ammonia and carbon-containing gas, the term "subset" refers to a subset of the resulting volume of the mixture. With regard to the fission gas mixture, the use of a subset occurs both when, with the composition of the fission gas mixture remaining unchanged, only a subset of the resulting volume of the fission gas mixture is used, and when not all components of the resulting fission gas mixture are used—for example, when an enrichment or depletion of a component takes place and the correspondingly enriched or depleted gas stream is fully or partially utilized.
[0046] Before being subjected to reforming conditions, additional gases can be added to the cracked gas mixture—or to the portion of it intended for the reforming conditions. For example, carbon-containing gas can be added; for example, natural gas can be added to the cracked gas mixture. This carbon-containing gas is then also reformed and contributes to the production of the reducing gas.
[0047] The reducing gas is the gas introduced into the reduction unit or its interior containing metal oxide material – where the reduction reactions take place – with its composition and temperature at the time of introduction. Before this composition and temperature are reached, a precursor of the reducing gas is present, on the basis of which the reducing gas is prepared. Preparation can be achieved, for example, by adding additional components or heating. Preparation can also be achieved through chemical reactions occurring in the precursor without external intervention, which, for example, change the chemical composition or the temperature.
[0048] The reduction unit is, for example, a reduction shaft—for example, when conducting a direct reduction process with a reduction shaft containing a fixed bed of metal oxide-containing material. The reduction unit is, for example, a fluidized-bed reactor—for example, when conducting a direct reduction process with a reduction unit containing a fluidized bed of metal oxide-containing material. The fluidized-bed reactor can also comprise several individual sub-reactors, which are connected, for example, in parallel or sequentially and together form the fluidized-bed reactor.
[0049] The reduction unit is, for example, a fluidized-bed reactor—for example, when conducting a direct reduction process with a reduction unit containing a fluidized bed of metal oxide-containing material. The fluidized-bed reactor can also comprise several individual sub-reactors, which are connected in parallel or sequentially, for example, and together form the fluidized-bed reactor.
[0050] The reduction unit can also be a blast furnace containing a fixed bed of metal oxide-containing material - in the operation of a blast furnace, ammonia can, for example, replace PCI coal or fossil reducing gases.
[0051] Advantageous effects of the invention
[0052] Ammonia cracking is a highly endothermic reaction (+93 kJ / mol). Ammonia cracking therefore leads to significant local temperature reductions, which are undesirable in neither a reforming device nor a reduction unit. Therefore, large amounts or concentrations of NH3 should not be present in the feed gas for the reforming device and the reduction gas to the reduction shaft.
[0053] For kinetic and thermodynamic reasons, steam reforming and CO2 reforming reactions (CH4+H2O^CO+3H2 and CH4+CO2^2CO+2H2) are carried out with catalysts at temperatures of 700–1150°C. If the temperature during ammonia cracking were in this range, this would lead to very rapid decomposition of the ammonia and thus to a rapid, sharp local temperature drop. A temperature drop can lead to adverse effects during reforming, such as reduced natural gas conversion or carbon deposits (CO+H2^C+H2O or 2CO—>C+CO2).
[0054] To avoid such adverse interactions between ammonia cracking and reforming, the ammonia cracking occurs before reforming. The heat required to maintain the endothermic ammonia cracking is supplied before reforming. Only after the ammonia cracking has occurred is the resulting cracked gas mixture subjected to reforming conditions at temperatures of 700-1150°C. According to a preferred embodiment, the mixture is heated before being subjected to ammonia cracking conditions.
[0055] Preheating the mixture has the advantage of creating favorable temperature conditions for ammonia decomposition. The energy supplied during heating is then already present in the mixture.
[0056] Energy supplied for heating can, for example, be fed into the reforming process by heat exchange with exhaust gas.
[0057] Instead or in addition, electrical energy, waste heat from the reduction unit, waste heat from a melting unit used to melt the reduction product, heat from the top gas, or steam generated by means of such heat sources can also be used.
[0058] According to a preferred embodiment, the mixture is first passed through an ammonia cracker, as seen in the flow direction of the mixture, and then the resulting cracked gas mixture is passed through a reforming device, optionally with heating.
[0059] Heating the cracked gas mixture before introducing it into a reforming device has the advantage of allowing favorable temperature conditions for reforming to be achieved. The energy supplied during heating is then already present in the cracked gas mixture upon introduction into the reforming device and does not need to be added to the reforming device.
[0060] Energy supplied for heating can, for example, be fed into the reforming process by heat exchange with exhaust gas.
[0061] Instead or in addition, electrical energy, waste heat from the reduction unit, waste heat from a melting unit used to melt the reduction product, heat from the top gas, or steam generated by means of such heat sources can also be used.
[0062] According to another preferred embodiment, the mixture is passed through at least one tube which contains both catalyst material for ammonia cracking and catalyst material for reforming, wherein, viewed in the flow direction of the mixture, the catalyst material for ammonia cracking is arranged upstream of the catalyst material for reforming.
[0063] According to one embodiment, the carbon-containing gas is heated during the preparation of the mixture, followed by the addition of ammonia. The ammonia may have already been heated, for example, by heat exchange with exhaust gas from the reforming process.
[0064] Instead or in addition, electrical energy, waste heat from the reduction unit, waste heat from a melting unit used to melt the reduction product, heat from the top gas, or steam generated by means of such heat sources can also be used.
[0065] According to one embodiment, the ammonia is heated during the preparation of the mixture and then added to the carbon-containing gas. For example, the ammonia can be heated by heat exchange with the exhaust gas from the reforming process. The carbon-containing gas may also have been heated previously, for example, by heat exchange with the exhaust gas from the reforming process.
[0066] Instead or in addition, electrical energy, waste heat from the reduction unit, waste heat from a melting unit used to melt the reduction product, heat from the top gas, or steam generated by means of such heat sources can also be used.
[0067] During the reduction of metal oxide-containing material, a top gas is produced, which can be used, at least in part, in the recovery of the reducing gas, possibly after processing. Processing may include, for example, dedusting, cooling, reducing and / or adjusting the water vapor content, and enriching or depleting components.
[0068] A top gas is discharged from the reduction unit. The top gas is formed from the reducing gas as it flows through the reduction unit due to the reactions taking place in the reduction unit between its components and the metal oxide-containing material or the products resulting from these reactions, such as the resulting metallic iron. Due to the reduction reactions taking place in the reduction unit, the top gas has less reducing power than the reducing gas. Part or all of the top gas can be used—if necessary after further processing—as a component in the preparation of the reducing gas.Utilization of a partial quantity occurs both when only a portion of the resulting top gas volume is used, with the composition of the top gas remaining unchanged, and when not all components of the resulting top gas are used—for example, when an enrichment of a component—for example, hydrogen enrichment—occurs and the correspondingly enriched gas stream is fully or partially utilized. According to a preferred embodiment, the processing takes place without reducing the carbon dioxide content.
[0069] According to a preferred embodiment, the nitrogen content is reduced during treatment. For this purpose, a device for separating nitrogen (N2) can be used, for example.
[0070] If only a portion of the top gas is used to produce the reducing gas, the amount of nitrogen that enters the reducing gas through recirculation is reduced because not all of the nitrogen contained in the top gas enters the reducing gas. Top gas that is not used as a component in the preparation of top gas can be used, for example, as a fuel component for the reforming device's burners.
[0071] According to a preferred embodiment, energy is supplied at least partially by electrical heating to create reforming conditions. Instead or additionally, waste heat from the reduction unit, or waste heat from a melting unit used to melt the reduction product, or heat from the top gas, or steam generated by such heat sources, can also be used.
[0072] According to a preferred embodiment, energy is supplied at least partially by electrical heating to create ammonia-splitting conditions. Instead or additionally, waste heat from the reduction unit, or waste heat from a melting unit used to melt the reduction product, or heat from the top gas, or steam generated by such heat sources, can also be used.
[0073] According to a preferred embodiment, heat is supplied to the ammonia cracking, which is extracted from the top gas.
[0074] According to a preferred embodiment, the proportions of ammonia and carbon-containing gas in the mixture can be changed.
[0075] When producing reducing gas, hydrogen (H2) can also be added to a precursor of the reducing gas. According to another preferred embodiment, the ratios of ammonia to hydrogen in the reducing gas can be varied. For example, the addition of hydrogen (H2) can be increased or decreased, or the amount of ammonia used can be increased or decreased. Heat generated during reforming can be used, for example, to support endothermic ammonia cracking reactions—for example, in an ammonia cracker that may be present or in a tube containing both catalyst material for ammonia cracking and catalyst material for reforming.Instead or in addition, electrical energy, waste heat from the reduction unit, waste heat from a melting unit used to melt the reduction product, heat from the top gas, or steam generated by means of such heat sources can also be used.
[0076] Heat generated during reforming is, for example, waste heat from the reforming process. Heat generated during reforming includes, for example, the following: During reforming, a hot exhaust gas is generated, for example, as a result of combustion processes carried out by burners that provide heat for the reforming process. The hot exhaust gas – which contains waste heat from the reforming process – can be utilized in such a way that its heat – i.e., waste heat from the reforming process – is used for ammonia cracking.
[0077] Waste heat can be supplied to the ammonia cracking process by thermal radiation and / or convection, for example when an ammonia cracking device is integrated into parts of a reforming device.
[0078] To support endothermic reforming reactions, the heat generated during reforming can be utilized. This can be done by heating the gas to be subjected to the reforming reactions, for example, the cracked gas mixture.
[0079] Instead or in addition, electrical energy, waste heat from the reduction unit, waste heat from a melting unit used to melt the reduction product, heat from the top gas, or steam generated by means of such heat sources can also be used.
[0080] Heat generated during reforming is, for example, waste heat from the reforming process. Heat generated during reforming includes, for example, the following: During reforming, hot exhaust gas is generated, for example, as a result of combustion processes carried out by burners that provide heat for the reforming process. The hot exhaust gas – which contains waste heat from the reforming process – can be utilized in such a way that its heat – i.e., waste heat from the reforming process – is utilized. Waste heat can be supplied to the system by thermal radiation and / or convection.
[0081] According to one variant, the cracked gas mixture intended for reforming conditions is heated before being subjected to reforming conditions. This prevents it from entering the reforming device too cold, which would otherwise lead to carbon deposits. For this heating, waste heat from the reforming device can be used, for example. Instead or in addition, electrical energy, waste heat from the reduction unit, waste heat from a melting unit used to melt the reduction product, heat from the top gas, or steam generated by such heat sources can also be used.
[0082] When heat is supplied by burners during reforming, flue gas is produced. Flue gas, or seal gas obtained from flue gas—an inert gas with a composition of, for example, approximately 78% N2, 20% CO2, 1% O2, 1% H2O—can contribute to heating to the temperature required for ammonia cracking (NH3). According to one embodiment, the heat supplied to the ammonia cracking is provided at least partially by the flue gas.
[0083] As a result of the reforming conditions, a so-called reforming gas is obtained. The reforming gas contributes to the reducing gas; the reforming gas can be the reducing gas or a precursor of the reducing gas.
[0084] In one variant, ammonia is added to the reforming gas. This ammonia can contribute to the reducing power of the reducing gas in addition to the reducing components present in the reforming gas.
[0085] Preferably, however, the majority of the ammonia used to obtain the reducing gas is used to produce the cracked gas mixture, and only a small part of the total ammonia quantity is added to the reforming gas.
[0086] The reforming gas may also contain ammonia because, as previously mentioned, the cracked gas mixture may still contain ammonia.
[0087] This ammonia content can be increased by adding ammonia to the reforming gas.
[0088] According to one variant, ammonia is added to the reduction unit in which the reduction of the metal oxide-containing material takes place—in addition to the introduction of the reducing gas; according to another embodiment, this is done independently of the introduction of the reducing gas. This ammonia can contribute to the reduction in addition to the reducing gas.
[0089] Preferably, however, the majority of the ammonia used is used to generate the cracked gas mixture, and only a small portion of the total ammonia quantity is added to the reduction unit. The NH3 concentration in the reduction gas should not exceed 8 vol%, particularly preferably 5 vol%.
[0090] According to one variant, the ammonia added to the reforming gas and / or the reduction unit is heated. For this purpose, waste heat from the reforming process can be used, for example. For example, pipe sections in a heat exchanger can be used for this purpose, which can also be used to heat top gas fuel by heat exchange with waste heat from the reforming device. Top gas fuel is a portion of the top gas that—possibly after processing—is used as a component of the fuel for the burners operated in a reforming device.
[0091] Instead or in addition, electrical energy, waste heat from the reduction unit, waste heat from a melting unit used to melt the reduction product, heat from the top gas, or steam generated by means of such heat sources can also be used.
[0092] Preferably, no reduction of the ammonia content is carried out in the cracked gas mixture or in the portion of the cracked gas mixture intended for reforming - for example in an NHs absorber or a so-called NHs stripper - the cracked gas mixture is fed directly to the reforming process.
[0093] Another object of the invention is a
[0094] Apparatus for reducing metal oxide-containing material, comprising:
[0095] - a reduction unit,
[0096] - a reducing gas inlet leading into the reduction unit,
[0097] - a supply line for carbon-containing gas,
[0098] - an ammonia feed line, characterized in that the feed line for carbon-containing gas and the ammonia feed line open into a mixture line, and the mixture line opens into a device for ammonia cracking, and from the ammonia cracking device a cracked gas mixture line extends, which opens into a reforming device for reforming carbon-containing gas, and from the reforming device a reforming gas line extends, which opens into the reducing gas inlet.
[0099] A method according to the invention can be carried out by means of such a device.
[0100] Existing devices for reducing metal oxide-containing material comprising a reforming device can be easily converted to a device according to the invention, whereby they become capable of carrying out a process according to the invention.
[0101] There may be one reduction unit or several reduction units.
[0102] There may be one reducing gas inlet or several reducing gas inlets.
[0103] There may be one carbon-containing gas supply line or several carbon-containing gas supply lines.
[0104] There may be one ammonia supply line or several ammonia supply lines.
[0105] There may be one mixture line or several mixture lines.
[0106] There may be one ammonia splitting device or several ammonia splitting devices.
[0107] There may be one fission gas mixture line or several fission gas mixture lines.
[0108] There may be one reforming device or several reforming devices.
[0109] There may be one reforming gas line or several reforming gas lines.
[0110] In the reduction unit, material containing metal oxide is reduced using a reducing gas.
[0111] The reducing gas is introduced into the reduction unit via the reducing gas inlet. The carbon-containing gas supply line carries carbon-containing gas. According to one embodiment, a heating device for heating the carbon-containing gas is provided in the carbon-containing gas supply line; for example, a heat exchanger, for example, for heat exchange with exhaust gas from the reforming process.
[0112] Instead or in addition, a heating device may be provided which uses electrical energy, waste heat from the reduction unit, or waste heat from a melting unit used to melt the product of the reduction, or heat from the top gas, or steam generated by means of such heat sources.
[0113] The ammonia supply line carries ammonia—pure or in an ammonia-containing gas mixture. According to one embodiment, a heating device for heating the ammonia is present in the ammonia supply line; for example, a heat exchanger, for example, for heat exchange with exhaust gas from the reforming process.
[0114] Instead or in addition, a heating device may be provided which uses electrical energy, waste heat from the reduction unit, or waste heat from a melting unit used to melt the product of the reduction, or heat from the top gas, or steam generated by means of such heat sources.
[0115] The carbon-containing gas supply line and the ammonia supply line flow into a mixture line. The mixture line serves to convey a mixture of carbon-containing gas and ammonia. The mixture line can include a gas mixer section; according to one variant, the carbon-containing gas supply line and the ammonia supply line flow into the gas mixer section, where mixing takes place using a gas mixer, and the resulting mixture is then passed through the mixture line.
[0116] According to one embodiment, a heating device for heating the mixture is provided in the mixture line; for example, a heat exchanger, for example for heat exchange with exhaust gas from the reforming.
[0117] Instead or additionally, a heating device may be present which uses electrical energy, waste heat from the reduction unit, or waste heat from a melting unit used to melt the reduction product, or heat from the top gas, or steam generated by such heat sources. The mixture line opens into an ammonia cracking device - the ammonia line device is thus supplied with mixture via the mixture line. In the ammonia cracking device, ammonia-splitting conditions prevail at a temperature in a range with a lower limit of 350°C, preferably 450°C, and an upper limit of 650°C, preferably 550°C. At least a portion of the ammonia in the mixture is cracked in the ammonia cracking device. A cracked gas mixture line leads from the ammonia cracking device.
[0118] According to one embodiment, a heating device for heating the cracked gas mixture is present in the cracked gas mixture line; for example, a heat exchanger, for example for heat exchange with exhaust gas from the reforming.
[0119] Instead or in addition, a heating device may be provided which uses electrical energy, waste heat from the reduction unit, or waste heat from a melting unit used to melt the product of the reduction, or heat from the top gas, or steam generated by means of such heat sources.
[0120] According to one embodiment, there is no device in the cracked gas mixture line to reduce the ammonia content.
[0121] According to one embodiment, there is no device for reducing the ammonia content downstream of the ammonia splitting device in the gas flow direction towards the reduction unit.
[0122] According to one embodiment, the device for ammonia decomposition comprises an electrical heating device. An electrical heating device heats using electrical energy.
[0123] Instead or in addition, a heating device may be provided which uses waste heat from the reduction unit, or waste heat from a melting unit used to melt the product of the reduction, or heat from the top gas, or steam generated by means of such heat sources.
[0124] According to one embodiment, the ammonia cracking device comprises a heat exchanger for exchanging heat with flue gas from the reforming device. If burners are used to supply heat in the reforming device, flue gas is produced. The flue gas can be discharged from the reforming device via a flue gas outlet. Heat from the flue gas can be used in the ammonia cracking process by routing the flue gas outlet through a heat exchanger of the ammonia cracking device. According to one embodiment, hot flue gas can be passed through the ammonia cracking device; for example, if the mixture flows through tubes filled with catalyst in the ammonia cracking device, flue gas can be bypassed around these tubes to transfer heat.
[0125] Waste heat from the reduction unit, or waste heat from a melting unit used to melt the reduction product, or heat from the top gas can also be used to supply heat to the ammonia cracking device.
[0126] Instead or in addition, electrical energy, waste heat from the reduction unit, waste heat from a melting unit used to melt the reduction product, heat from the top gas, or steam generated by means of such heat sources can also be used.
[0127] The cracked gas mixture line flows into a reforming device. The cracked gas mixture produced in the ammonia cracking device is fed to the reforming device via the cracked gas mixture line. Reforming conditions prevail in the reforming device at a temperature ranging from a lower limit of 700°C to an upper limit of 1150°C, preferably 1000°C. At least a portion of the carbon-containing gas in the cracked gas mixture is reformed in the reforming device. Reforming gas is obtained in the reforming device. A reforming gas line leads from the reforming device.
[0128] According to one embodiment, the reforming device comprises an electrical heating device.
[0129] Instead or in addition, a heating device may be provided which uses waste heat from the reduction unit, or waste heat from a melting unit used to melt the product of the reduction, or heat from the top gas, or steam generated by means of such heat sources.
[0130] According to one embodiment, the ammonia cracking device is designed as an ammonia cracker; an ammonia cracker is a separate device from a reforming device. According to one embodiment, the ammonia cracking device is designed to be integrated into parts of the reforming device.
[0131] A reforming device is, for example, a reformer comprising several tubes containing catalyst material for reforming. The ammonia cracking device can then be integrated, for example, into parts of the reforming device by reformer tubes containing both catalyst material for ammonia cracking and catalyst material for reforming, with the catalyst material for ammonia cracking being arranged upstream of the catalyst material for reforming, as seen in the flow direction of the mixture.
[0132] According to one embodiment, the device for reducing metal oxide-containing material comprises a top gas discharge for discharging top gas from the reduction unit.
[0133] According to a preferred embodiment, the top gas outlet opens into the supply line for carbon-containing gas.
[0134] According to one embodiment, the top gas outlet contains at least one processing device. A processing device is used to perform, for example, dedusting, cooling, reducing and / or adjusting the water vapor content, and enriching or depleting components.
[0135] Preferably, the top gas outlet does not contain a device for reducing the carbon dioxide content.
[0136] Preferably, the top gas outlet contains at least one device for separating nitrogen N2.
[0137] Preferably, at least one fuel line for supplying top gas as a fuel component for burners of the reforming device extends from the top gas outlet.
[0138] According to a preferred embodiment, the device for reducing metal oxide-containing material comprises a device for controlling and / or regulating the proportions of ammonia and carbon-containing gas in the mixture. Such a device comprises sensors for determining the content of ammonia and carbon-containing gas in the mixture.
[0139] According to a preferred embodiment, the device for reducing metal oxide-containing material comprises a device for controlling and / or regulating the quantitative ratios of ammonia and hydrogen in the reducing gas. Such a device comprises sensors for determining the ammonia and hydrogen content in the reducing gas.
[0140] According to a preferred embodiment, the device for reducing metal oxide-containing material comprises at least one hydrogen addition line for adding hydrogen H2 to the reforming gas line. The hydrogen addition line opens into the reforming gas line.
[0141] According to a preferred embodiment, the device for reducing metal oxide-containing material comprises at least one ammonia addition line for adding ammonia to the reforming gas line. The ammonia addition line opens into the reforming gas line.
[0142] According to a preferred embodiment, the device for reducing metal oxide-containing material comprises at least one ammonia supply line for adding ammonia to the reduction unit—in addition to the introduction of the reducing gas or in addition to the introduction of the reducing gas; this addition of ammonia to the reduction unit can occur independently of the introduction of the reducing gas. The ammonia supply line opens into the reduction unit.
[0143] According to one variant, a heating device for heating the ammonia is provided in the ammonia supply line; for example, a heat exchanger, for example, for heat exchange with the exhaust gas from the reforming process. For example, pipe sections in a heat exchanger can be used to utilize the waste heat from the reforming process, which can also be used to heat top gas fuel by heat exchange with waste heat from the reformer.
[0144] Instead or in addition, a heating device may be provided which uses electrical energy, waste heat from the reduction unit, or waste heat from a melting unit used to melt the product of the reduction, or heat from the top gas, or steam generated by means of such heat sources.
[0145] A further subject matter of the present application is a signal processing device with a machine-readable program code, characterized in that it comprises control and / or regulating commands for carrying out a method according to the invention. A further subject matter is a signal processing device for carrying out a method according to one of claims 1 to 8. A further subject matter of the present application is a machine-readable program code for a signal processing device, characterized in that the program code comprises control and / or regulating commands that cause the signal processing device to carry out a method according to the invention.A further subject matter is a computer program product comprising instructions for a signal processing device which, when the program for the signal processing device is executed, cause the signal processing device to carry out the method according to one of claims 1 to 8.
[0146] A further subject matter of the present application is a storage medium having a machine-readable program code according to the invention stored thereon. A further subject matter is a storage medium having a computer program stored thereon for carrying out a method according to one of claims 1 to 8.
[0147] Short description of the drawings
[0148] The present invention is described below by way of example with reference to several schematic figures.
[0149] Figure 1 shows schematically the implementation of a variant of the method according to the invention in a variant of the device according to the invention for reducing metal oxide-containing material.
[0150] Figure 2 shows schematically another variant.
[0151] Figure 3 shows another variant.
[0152] Figure 4 shows schematically another variant.
[0153] Figure 5 shows schematically another variant.
[0154] Description of the embodiments
[0155] Examples
[0156] Figure 1 schematically shows an apparatus 10 for reducing metal oxide-containing material 20. Metal oxide-containing material 20 is fed into the reduction unit 30. Reducing gas is introduced via the reducing gas inlet 40 leading into the reduction unit 30 in order to reduce the metal oxide-containing material 20. The reducing gas is obtained using ammonia NH3 and carbon-containing gas. For this purpose, a mixture comprising ammonia and carbon-containing gas is prepared. For this purpose, the feed line 50 for carbon-containing gas and the ammonia feed line 60 open into a mixture line 70. The mixture line 70 opens into an ammonia cracking device 80. In the ammonia cracking device 80, at least a portion of the mixture is exposed to ammonia-splitting conditions at a temperature in a range with a lower limit of 350°C, preferably 450°C, and an upper limit of 650°C, preferably 550°C.This creates a cracked gas mixture. The cracked gas mixture line 90 extends from the ammonia cracking device and flows into the reforming device 100. At least a portion of the cracked gas mixture is subjected to reforming conditions in the reforming device 100 at a temperature in a range with a lower limit of 700°C and an upper limit of 1150°C, preferably 1000°C. The reforming gas produced is fed into the reducing gas inlet 40 via the reforming gas line 110 extending from the reforming device 100. The reforming gas line 110 flows into the reducing gas inlet 40.
[0157] In the supply line 50 for carbon-containing gas, a heating device for heating the carbon-containing gas may be present, but this is not shown separately for the sake of clarity.
[0158] The ammonia supply line 60 carries ammonia. According to one embodiment, a heating device for heating the ammonia is provided in the ammonia supply line, although this is not shown separately for clarity.
[0159] The supply line 50 for carbon-containing gas and the ammonia supply line 60 open into a mixture line 70. The mixture line 70 may include a gas mixer section; however, this is not shown separately for clarity. The mixture line 70 opens into an ammonia cracking device 80—the ammonia cracking device 80 is thus supplied with the mixture via the mixture line 70. At least a portion of the ammonia in the mixture is cracked in the ammonia cracking device 80. A cracked gas mixture line 90 extends from the ammonia cracking device 80.
[0160] The ammonia cracking device 80 may comprise an electrical heating device 81; the optionally present electrical heating device 81 is schematically represented by a lightning bolt. Optionally, instead of or in addition to this, a heating device may also be present that uses waste heat from the reduction unit, or waste heat from a melting unit used to melt the reduction product, or heat from the top gas, or steam generated by such heat sources, for heating purposes. However, this is not shown separately for clarity.
[0161] Optionally, the ammonia cracking device may also comprise, in addition to or instead of, a heat exchanger for heat exchange with flue gas from the reforming device, which is not shown separately for the sake of clarity.
[0162] A heating device for heating the mixture can optionally be present in the mixture line 70; this is shown in Figure 1 as an optionally present and therefore dashed-bordered heat exchanger 120 for heat exchange with exhaust gas 130 from the reforming - shown as a jagged arrow.
[0163] A heating device for heating the cracked gas mixture can optionally be present in the cracked gas mixture line 90; this is shown in Figure 1 as an optionally present and therefore dashed-bordered heat exchanger 120 for heat exchange with exhaust gas 130 from the reforming - shown as a jagged arrow.
[0164] There is no device in the cracked gas mixture line 90 to reduce the ammonia content.
[0165] In the device 10 for reducing metal oxide-containing material 20, there is no device for reducing the ammonia content in the gas flow direction towards the reduction unit 30 after the device for splitting ammonia 80.
[0166] The reforming device 100 may include an electrical heating device 101; the optionally present electrical heating device 101 is schematically represented by a lightning bolt.
[0167] Instead or in addition, a heating device may be present which uses waste heat from the reduction unit, or waste heat from a melting unit used to melt the product of the reduction, or heat from the top gas, or steam generated by means of such heat sources, but this is not shown separately for the sake of clarity.
[0168] In Figure 1, the ammonia cracking device 80 is designed as an ammonia cracker separate from a reforming device 100. Figure 2 shows a design largely identical to Figure 1, but differing in the design of the ammonia cracking device 80. Schematically shown is a design of the ammonia cracking device 80 as integrated into parts of the reforming device 100. The reforming device 100 is a reformer comprising several tubes containing catalyst material for reforming; a tube 91 is shown. The upper region 92 of the tube 91 contains catalyst material for reforming, and the lower region 93 of the tube contains catalyst material for ammonia cracking. Viewed in the flow direction of the mixture towards the reduction unit 30, the catalyst material for ammonia cracking is arranged upstream of the catalyst material for reforming.
[0169] Figure 3 shows a design largely identical to Figure 1. Additionally, a variant is shown in which a top gas outlet 140 is provided for discharging top gas from the reduction unit 30. The top gas outlet 140 opens into the supply line 50 for carbon-containing gas. Also shown is an optional—and therefore shown in dashed lines—treatment device 150, in this case a dust removal device. The top gas outlet 140 does not contain a device for reducing the carbon dioxide content.
[0170] The top gas outlet 140 may contain a device for separating nitrogen N2, which is not shown separately for the sake of clarity.
[0171] A fuel line for supplying top gas as a fuel component for burners of the reforming device 100 can originate from the top gas outlet, but this is not shown separately for the sake of clarity.
[0172] Figure 4 shows a design largely identical to Figure 1. The additional features shown will now be discussed:
[0173] - The device 10 for reducing metal oxide-containing material 20 also includes a device 160 for controlling and / or regulating the proportions of ammonia and carbon-containing gas in the mixture. Also shown is its sensor 170 for determining the content of ammonia and carbon-containing gas in the mixture.
[0174] - The device 10 for reducing metal oxide-containing material 20 also includes a device 180 for controlling and / or regulating the proportions of ammonia and hydrogen in the reducing gas. Also shown is its sensor 190 for determining the ammonia and hydrogen content in the reducing gas.
[0175] - The device 10 for reducing metal oxide-containing material 20 also includes a hydrogen addition line 200 for adding hydrogen H2 to the reforming gas line 110. The hydrogen addition line 200 opens into the reforming gas line 110. - The device 10 for reducing metal oxide-containing material 20 also includes an ammonia addition line 210 for adding ammonia to the reforming gas line 110. The ammonia addition line 210 opens into the reforming gas line 110.
[0176] - The device 10 for reducing metal oxide-containing material 20 also includes an ammonia supply line 220 for adding ammonia to the reduction unit 30. The ammonia supply line 220 opens into the reduction unit 30, in addition to the reducing gas inlet 40; the addition of ammonia to the reduction unit via the ammonia supply line 220 occurs independently of the introduction of the reducing gas into the reduction unit 30.
[0177] A heating device for heating the ammonia can be present in the ammonia supply line 220; for example, a heat exchanger, for example, for heat exchange with exhaust gas from the reforming process. For example, line sections in a heat exchanger can be used to utilize the waste heat from the reforming process, which can also be used to heat top gas fuel by heat exchange with waste heat from the reformer.
[0178] Waste heat from the reduction unit, waste heat from a melting unit used to melt the reduction product, or heat from the top gas can also be utilized. However, these are not shown separately for clarity.
[0179] Instead or in addition, a heating device may be present that uses electrical energy, waste heat from the reduction unit, or waste heat from a melting unit used to melt the reduction product, or heat from the top gas, or steam generated by such heat sources. However, this is not shown separately for clarity.
[0180] Figure 5 schematically shows, based on Figure 1, how flue gas 130 discharged from the reforming device 100 via a flue gas outlet can be used in the ammonia cracking process in the ammonia cracking device 230. Hot flue gas is passed through the ammonia cracking device 230, in which the mixture flows through tubes 240 filled with catalyst. The flue gas 230 is guided around these tubes to transfer heat. List of reference symbols
[0181] 10 Device for reduction
[0182] 20 metal oxide-containing material
[0183] 30 Reduction unit
[0184] 40 Reducing gas introduction
[0185] 50 Supply line for carbon-containing gas
[0186] 60 Ammonia supply line
[0187] 70 mixture line
[0188] 80 Device for ammonia splitting
[0189] 81 Electric heating device
[0190] 90 cracked gas mixture line
[0191] 91 pipe
[0192] 92 upper area
[0193] 93 lower area
[0194] 100 reforming device
[0195] 101 Electric heating device
[0196] 110 Reforming gas line
[0197] 120 heat exchangers
[0198] 130 Exhaust gas from reforming
[0199] 140 Top gas discharge
[0200] 150 processing device
[0201] 160 Device for controlling and / or regulating the proportions (of ammonia and carbon-containing gas in the mixture)
[0202] 170 sensors
[0203] 180 Device for controlling and / or regulating the proportions (of ammonia and hydrogen in the reducing gas)
[0204] 190 Sensor
[0205] 200 Hydrogen addition line
[0206] 210 Ammonia addition line
[0207] 220 Ammonia supply line
[0208] 230 Device for ammonia splitting
[0209] 240 pipe
Claims
1. A method for reducing a material containing a metal oxide, which uses a reducing gas obtained using ammonia NH3 and carbon-containing gas by introducing it into a reduction unit, characterized in that, when obtaining the reducing gas, a mixture containing ammonia and a carbon-containing gas is prepared, and at least part of the mixture is first subjected to ammonia cracking conditions at a temperature in the range with a lower limit of 350°C, preferably 450°C, and an upper limit of 650°C, preferably 550°C, wherein a cracking gas mixture is formed, and then at least part of the cracking gas mixture is subjected to reforming conditions at a temperature in the range with a lower limit of 700°C and an upper limit of 1150°C, preferably 1000°C, for reforming the carbon-containing gas, wherein the reforming gas obtained after passing through the reforming conditions contributes to the formation of the reducing gas, wherein the reforming is carried out as steam reforming and / or as CO2 reforming.
2. The method according to claim 1, characterized in that the mixture, when viewed in the direction of the mixture flow, is first passed through an ammonia cracking device, and then the cracking gas mixture thus obtained is passed through a reforming device (100).
3. The method according to claim 1, characterized in that the mixture is passed through at least one tube that contains both the catalytic material for cracking ammonia and the catalytic material for reforming, and when viewed in the direction of flow of the mixture, the catalytic material for cracking ammonia is located before the catalytic material for reforming.
4. The method according to any one of paragraphs 1-3, in which part of the exhaust gas or all of the exhaust gas after treatment is used as a component in the preparation of a reducing gas, characterized in that the treatment is carried out without reducing the carbon dioxide content.
5. The method according to any one of paragraphs 1-4, in which part of the exhaust gas or all of the exhaust gas after treatment is used as a component in the preparation of a reducing gas, characterized in that the nitrogen content is reduced during treatment.
6. The method according to any one of paragraphs 1-5, characterized in that the heat released during the reforming process is used to maintain endothermic ammonia cracking reactions.
7. The method according to any one of paragraphs 1-6, in which the reduction of the material containing the metal oxide is carried out in a reduction unit (30), characterized in that ammonia is added to the reduction unit (30) in addition to the introduction of the reducing gas.
8. The method according to any one of paragraphs 1-7, characterized in that the ammonia content in the cracking gas mixture or in the part of the cracking gas mixture intended for reforming is not reduced.
9. A device (10) for reducing a material (20) containing a metal oxide, comprising recovery unit (30), line (40) for reducing gas entering the reduction unit (30), supply (50) for carbon-containing gas, supply (60) of ammonia, characterized in that the inlet (50) for the carbon-containing gas and the inlet (60) for the ammonia enter into a line (70) for the mixture, and the line (70) for the mixture enters into a device (80) for cracking ammonia, and from the device (80) for cracking ammonia there is a line (90) for the cracking gas mixture, which enters into a reforming device (100) for reforming the carbon-containing gas, and from the reforming device (100) there is a line (110) for the reforming gas, which enters into a line (40) for the reducing gas, wherein the reforming is steam reforming and / or CO2 reforming.
10. The device according to claim 9, characterized in that the device (80) for cracking ammonia contains a heat exchanger (120) for heat exchange with the flue gas from the reforming device (100).
11. The device according to paragraph 9 or 10, characterized in that the device (80) for cracking ammonia is made in the form of an ammonia splitter.
12. The device according to claim 9 or 10, characterized in that the device (80) for cracking ammonia is integrated into parts of the reforming device (100).
13. A device according to any one of paragraphs 9-12 with an upper gas outlet (140) for removing exhaust gas from the recovery unit (30), characterized in that the upper gas outlet (140) does not contain a device for reducing the carbon dioxide content.
14. A device according to any one of paragraphs 9-13 with an upper gas outlet (140) for removing exhaust gas from the recovery unit (30), characterized in that the upper gas outlet (140) contains at least one device for separating nitrogen N 2.
15. The device according to any one of paragraphs 9-14, characterized in that it includes at least one line (220) for feeding ammonia for adding ammonia to the recovery unit (30).