RESTORATION OF METAL OXIDE-CONTAINING MATERIALS 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
- 2026-07-01
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-based reduction processes face challenges in maintaining thermodynamic and kinetic conditions required for efficient reduction.
A process that utilizes a reduction gas obtained by combining ammonia (NH3) with carbon-containing gases, where ammonia is split to produce nitrogen and hydrogen, and the resulting gases are reformed with carbon-containing gases to create a unified gas flow that contributes to the reduction of metal oxide-containing materials. This process ensures efficient energy use by heating the ammonia splitting process with waste heat from reforming.
This approach reduces CO2 emissions by using ammonia and carbon-containing gases efficiently, while also addressing the challenges of hydrogen storage and transport. The process maintains favorable thermodynamic and kinetic conditions for the reduction reactions, enhancing the overall efficiency of the metal oxide reduction process.
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, wherein during the production of the reducing gas a first gas stream which contains ammonia is subjected to ammonia cracking, thereby forming a cracking gas stream, and a second gas stream which contains carbon is subjected to reforming, thereby forming a reforming gas stream, and combining at least a portion of the cracking gas stream and at least a portion of the reforming gas stream takes place, and this combining gas stream obtained during the combining makes a contribution to the reducing gas, characterized in that heat which arises during the reforming is supplied to the ammonia cracking.
[0024] The metal oxide-containing material is preferably iron oxide-containing material.
[0025] The reduction process, for example, is a direct reduction process. The reducing gas is obtained using ammonia NH3, and 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 hydrogen H2 cleavage product obtained from ammonia cleavage—alone or together with the nitrogen N2 cleavage product—mixed with one or more other gases.
[0027] The first gas stream can be pure ammonia or it can be a gas mixture containing ammonia.
[0028] The reducing gas can therefore contain ammonia; it consists partly of ammonia and additionally of other components.
[0029] 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.
[0030] According to the invention, reducing gas is obtained using ammonia by splitting ammonia and contributing the resulting splitting gas stream comprising nitrogen and hydrogen and optionally ammonia - optionally after enrichment of hydrogen or depletion of nitrogen - to the reducing gas.
[0031] 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.
[0032] Ammonia cracking takes place 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, under ammonia-cracking conditions. To achieve ammonia cracking, catalysts are used that catalyze ammonia cracking in this temperature range. This produces a cracking gas stream comprising nitrogen and hydrogen—and optionally ammonia. The cracking gas stream also contains ammonia if not all of the ammonia in the first gas stream is converted under the ammonia-cracking conditions, but only a portion of the ammonia in the first gas stream. The unreacted remainder of the ammonia from the first gas stream is then present in the cracking gas stream as ammonia. An ammonia content of up to 10 vol%, preferably up to 8 vol%, particularly preferably up to 6 vol% in the cracking gas stream is acceptable.
[0033] 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.
[0034] The reducing gas is obtained using a carbon-containing gas stream – this is the second gas stream. It contains 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.
[0035] A carbon-containing gas used can, for example, be natural gas or top gas discharged from the reduction unit - possibly after processing.
[0036] The carbon-containing gas contributes to the reducing gas, this contribution being in addition to the contribution to the reducing gas made by ammonia.
[0037] 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 with reforming of carbon-containing gas. It 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. Reforming is understood to mean the reforming of carbon-containing gas. Reforming conditions are understood to mean conditions under which reforming of carbon-containing gas takes place.Reforming conditions exist in a reforming device, making it suitable for reforming carbon-containing gas. To achieve these reforming conditions, catalysts are used that catalyze reforming in this temperature range—called reforming catalysts. Direct reduced iron (DRI) can also act as a reforming catalyst.
[0038] The reforming takes place, for example, as steam reforming and / or CO2 reforming according to
[0039] CH4+H2O— >CO+3H2
[0040] CH4+CO2^2CO+2H2.
[0041] This is illustrated using methane CH4 as an example; for higher hydrocarbon compounds, the reforming process is analogous.
[0042] In obtaining the reducing gas, at least a portion of the cracking gas stream and at least a portion of the reforming gas stream are combined. According to the invention, heat generated during the reforming is added to the ammonia cracking process, which produces the cracking gas stream.
[0043] With regard to the fission gas stream, use of a partial quantity occurs both when, with the composition of the fission gas stream remaining unchanged, only a partial quantity of the resulting volume of the fission gas stream is used, and when not all components of the resulting fission gas stream are used - for example, when an enrichment or depletion of a component takes place and the correspondingly enriched or depleted gas stream is used completely or partially.
[0044] With regard to the reforming gas stream, use of a partial quantity occurs both when, with the composition of the reforming gas stream remaining unchanged, only a partial quantity of the resulting volume of the reforming gas stream is used, and when not all components of the resulting reforming gas stream are used - for example, when an enrichment or depletion of a component takes place and the correspondingly enriched or depleted gas stream is used completely or partially.
[0045] 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.
[0046] 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.
[0047] 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.
[0048] 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.
[0049] Advantageous effects of the invention
[0050] Ammonia cracking is a highly endothermic reaction (+93 kJ / mol). Therefore, ammonia cracking leads to significant local temperature reductions, which are undesirable in neither a reforming device nor a reduction unit.
[0051] 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).
[0052] To avoid such adverse interactions between ammonia cracking and reforming, ammonia cracking and reforming are carried out using different gas streams – the first, ammonia-containing gas stream, and the second, carbon-containing gas stream. The two resulting gas streams – cracking gas stream and reforming gas stream – are then combined. According to the invention, the heat generated during reforming contributes to the energy required to maintain the endothermic ammonia cracking. Thus, ammonia cracking and reforming interact not only materially but also energetically in the production of the reducing gas, allowing the process to be carried out efficiently. 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 used in such a way that its heat – i.e. waste heat from the reforming process – is used for ammonia cracking.
[0053] If an ammonia cracking device is integrated into parts of a reforming device, waste heat can be supplied to the ammonia cracking process by thermal radiation and / or convection.
[0054] To support the endothermic ammonia cracking process, waste heat from the reduction unit in which the reduction is carried out, or waste heat from a melting unit used to melt the reduction product, or electrical energy, or steam generated by such heat sources can also be used—in addition to the heat generated during reforming, or instead of such heat. If precursors of the reducing gas are heated by gas heaters, waste heat from the gas heaters or steam generated by such heat sources can also be used.
[0055] For example, if the product of reduction - for example DRI direct reduced iron or sponge iron - is melted during steel production in a melting unit - for example an EAF, OBF, submerged arc furnace, smelter - and an exhaust gas is produced in the process, heat can be added to the ammonia cracking process, which is extracted from the exhaust gas of the melting unit.
[0056] 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.
[0057] Reforming is carried out in a reforming device.
[0058] 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.
[0059] 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.
[0060] 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.
[0061] 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.
[0062] According to a preferred embodiment, energy is supplied at least partially by electrical heating during ammonia cracking. Instead or in addition, 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. If precursors of the reducing gas are heated by gas heaters, waste heat from the gas heaters, or steam generated by such heat sources, can also be used.
[0063] According to a preferred embodiment, heat is supplied to the ammonia cracking, which is extracted from the top gas.
[0064] According to a preferred embodiment, heat is supplied to the ammonia cracking indirectly, for example via heat exchangers or via a heat transfer medium - for example steam.
[0065] According to a preferred embodiment, energy is supplied during reforming at least partially by electrical heating. Instead or additionally, waste heat from the reduction unit, or waste heat from a melting unit used to melt the reduction product, or waste heat from the reforming device, or heat from the top gas, or steam generated by such heat sources, can also be used. If precursors of the reducing gas are heated by gas heaters, waste heat from the gas heaters, or steam generated by such heat sources, can also be used. According to a preferred embodiment, the first gas stream is heated before being subjected to ammonia cracking.
[0066] Heating the first gas stream before ammonia cracking has the advantage of creating favorable temperature conditions for ammonia cracking. The energy supplied during heating is then already present in the first gas stream. Energy supplied to heat the first gas stream can be transferred to the reforming process, for example, by heat exchange with exhaust gas.
[0067] Instead of or in addition to this, 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. If precursors of the reducing gas are heated by gas heaters, waste heat from the gas heaters or steam generated by such heat sources can also be used.
[0068] According to a preferred embodiment, the second gas stream is heated before being subjected to reforming.
[0069] Heating the second gas stream prior to reforming has the advantage of allowing favorable temperature conditions for reforming. The energy supplied during heating is then already present in the second gas stream and does not need to be added during reforming. This prevents the gas stream from entering the reforming device too cold, which would otherwise lead to carbon deposits.
[0070] Energy supplied for heating can, for example, be fed into the reforming process by heat exchange with exhaust gas.
[0071] Instead of or in addition to this, electrical energy, waste heat from the reduction unit, waste heat from a melting unit used to melt the reduction product, waste heat from the reforming device, or heat from the top gas, or steam generated by such heat sources, can also be used. If precursors of the reducing gas are heated by gas heaters, waste heat from the gas heaters or steam generated by such heat sources can also be used.
[0072] According to a preferred embodiment, the ratios of the cracking gas stream and the reforming gas stream can be varied during the combination. 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 and 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.
[0073] The combination of the fission gas stream and the reforming gas stream produces a blend gas stream. The blend gas stream contributes to the reducing gas; the blend gas stream can be the reducing gas or a precursor to the reducing gas.
[0074] According to one variant, ammonia is added to the blending gas stream during the production of the reducing gas. This ammonia can contribute to the reducing power of the reducing gas in addition to the reducing components present in the blending gas stream.
[0075] Preferably, however, the majority of the ammonia used to obtain the reducing gas is used in the cracking gas stream, and only a small part of the total ammonia quantity is added to the combining gas stream.
[0076] The combination gas stream may also contain ammonia because, as previously mentioned, the fission gas stream, for example, may still contain ammonia.
[0077] This ammonia content can be increased by adding ammonia to the blending gas stream.
[0078] 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.
[0079] Preferably, however, the majority of the ammonia used is used to generate the cracking gas stream, and only a small part of the total ammonia quantity is added to the reduction unit.
[0080] The NH3 concentration in the reducing gas should not exceed 10 vol%, preferably not exceed 8 vol%, particularly preferably not exceed e vol%.
[0081] According to one variant, the ammonia added to the blending gas stream 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.
[0082] Instead of or in addition to this, 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. If precursors of the reducing gas are heated by gas heaters, waste heat from the gas heaters or steam generated by such heat sources can also be used.
[0083] Preferably, no reduction of the ammonia content is carried out in the cracking gas stream or in the portion of the cracking gas stream intended for combination with at least a portion of the reforming gas stream - for example in an NH3 absorber or a so-called NH3 stripper - the feed to the combination takes place directly in this regard.
[0084] Another object of the invention is a
[0085] Apparatus for reducing metal oxide-containing material, comprising:
[0086] - a reduction unit,
[0087] - a reducing gas inlet leading into the reduction unit,
[0088] - a first gas flow line for ammonia-containing gas,
[0089] - a second gas flow pipeline for carbon-containing gas,
[0090] - a device for splitting ammonia,
[0091] - a reforming device,
[0092] - a fission gas flow line,
[0093] - a reforming gas flow line,
[0094] - a combining gas flow line, wherein the first gas flow line opens into the ammonia cracking device, and the second gas flow line opens into the reforming device, and the cracking gas flow line starts from the ammonia cracking device, and the reforming gas flow line starts from the reforming device, and the cracking gas flow line and the reforming gas flow line open into the combining gas flow line, and the combining gas flow line (90) has an opening into the reducing gas inlet (40), characterized in that a heat supply device is provided for supplying heat generated during reforming in the reforming device to the ammonia cracking device.
[0095] A method according to the invention can be carried out by means of such a device.
[0096] 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.
[0097] There may be one reduction unit or several reduction units.
[0098] There may be one reducing gas inlet or several reducing gas inlets.
[0099] There may be one ammonia splitting device or several ammonia splitting devices.
[0100] There may be one reforming device or several reforming devices.
[0101] The reforming device can be internal or external. If it is internal, it also processes top gas from the reduction unit; the top gas is thus an internal source of carbon-containing gas with respect to the process. If it is external, it does not process top gas, but only carbon-containing gas supplied from external sources.
[0102] One or more gas heaters may be present to heat precursors of the reducing gas.
[0103] There may be one fission gas flow line or several fission gas flow lines.
[0104] There may be one reforming gas stream line or multiple reforming gas stream lines. There may be one combining gas stream line or multiple combining gas stream lines.
[0105] The combination gas flow line has an opening into the reducing gas inlet.
[0106] In the reduction unit, material containing metal oxide is reduced using a reducing gas.
[0107] The reducing gas is introduced into the reduction unit via the reducing gas inlet.
[0108] The first gas flow line carries ammonia-containing gas. According to one embodiment, a heating device for heating the ammonia-containing gas is present in the first gas flow line; for example, a heat exchanger, for example, for heat exchange with exhaust gas from the reforming process.
[0109] 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. If precursors of the reducing gas are heated by gas heaters, waste heat from the gas heaters or steam generated by such heat sources can also be used.
[0110] The first gas flow line leads into an ammonia cracking device. Ammonia-containing gas is thus supplied to the ammonia cracking device via the first gas flow 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 ammonia-containing gas is cracked in the ammonia cracking device, producing cracking gas. A cracking gas flow line leads from the ammonia cracking device.
[0111] The second gas flow line carries carbon-containing gas. According to one embodiment, a heating device for heating the carbon-containing gas is present in the second gas flow 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 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. If precursors of the reducing gas are heated by gas heaters, waste heat from the gas heaters or steam generated by such heat sources can also be used.
[0113] The second gas flow line flows into a reforming device—carbon-containing gas is thus supplied to the reforming device via the second gas flow 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 is reformed in the reforming device. Reforming gas is obtained in the reforming device. A reforming gas flow line leads from the reforming device.
[0114] According to one embodiment, a heating device for heating the fission gas stream is present in the fission gas stream line; for example, a heat exchanger, for example for heat exchange with exhaust gas from the reforming.
[0115] 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. If precursors of the reducing gas are heated by gas heaters, waste heat from the gas heaters or steam generated by such heat sources can also be used.
[0116] According to one embodiment, a heating device for heating the reforming gas stream is present in the reforming gas stream 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 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. If precursors of the reduction gas are heated by gas heaters, waste heat from the gas heaters or steam generated by such heat sources can also be used. The fission gas stream line and the reforming gas stream line flow into a combination gas stream line. The combination gas stream line serves to convey a mixture of fission gas stream and reforming gas stream.The combination gas stream line may comprise a gas mixer section; according to one variant, the fission gas stream line and the reforming gas stream line open into the gas mixer section, where the fission gas stream and the reforming gas stream combine and are mixed by means of a gas mixer, and the resulting mixture is passed on in the combination gas stream line.
[0118] According to one embodiment, a heating device for heating the combining gas stream is present in the combining gas stream 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 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. If precursors of the reducing gas are heated by gas heaters, waste heat from the gas heaters or steam generated by such heat sources can also be used.
[0120] According to one embodiment, there is no device in the cracking gas flow line for reducing 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] The device according to the invention is characterized in that a heat supply device is provided for supplying heat generated during reforming in the reforming device to the ammonia cracking device.
[0123] According to one embodiment, the ammonia cracking device comprises a heat exchanger for exchanging heat with flue gas from the reforming device as a heat supply device for supplying heat generated during reforming in the reforming device to the ammonia cracking device. If burners are used in the reforming device to supply heat, 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 cracking of the ammonia by guiding 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 passed around these tubes to transfer heat.
[0124] 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.
[0125] Instead of or in addition to this, 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. If precursors of the reducing gas are heated by gas heaters, waste heat from the gas heaters or steam generated by such heat sources can also be used.
[0126] According to one embodiment, the device for ammonia decomposition comprises an electrical heating device. An electrical heating device heats using electrical energy.
[0127] Instead or in addition, a heating device may be provided that utilizes 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. If precursors of the reducing gas are heated by gas heaters, waste heat from the gas heaters or steam generated by such heat sources can also be utilized.
[0128] According to one embodiment, the device for ammonia cracking is designed as an ammonia cracker; an ammonia cracker is a device separate from a reforming device.
[0129] According to one embodiment, the device for ammonia splitting is designed to be integrated into parts of the reforming device.
[0130] A reforming device is, for example, a reformer comprising several tubes containing catalyst material for reforming within a housing. The ammonia cracking device can then, for example, be integrated into parts of the reforming device or reformer by arranging tubes containing catalyst material for ammonia cracking—which constitute an ammonia cracking device—also within the reformer's housing. When burners are used to supply heat for reforming, flue gas is produced from the combustion processes. This exhaust gas from the reforming process can flow around the tubes of the ammonia cracking device containing catalyst material for ammonia cracking, which are arranged in the housing—and thereby supply heat to the ammonia cracking device.
[0131] According to one embodiment, the reforming device comprises an electric heating device. An electric heating device heats using electrical energy.
[0132] Instead or in addition, a heating device may be provided that utilizes 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. If precursors of the reducing gas are heated by gas heaters, waste heat from the gas heaters or steam generated by such heat sources can also be utilized.
[0133] 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.
[0134] According to a preferred embodiment, the top gas outlet opens into the second gas flow line for carbon-containing gas.
[0135] 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.
[0136] Preferably, the top gas outlet does not contain a device for reducing the carbon dioxide content. 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 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.
[0139] 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 combining gas flow line. The hydrogen addition line opens into the combining gas flow line.
[0140] 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 combining gas stream line. The ammonia addition line opens into the combining gas stream line.
[0141] 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.
[0142] 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.
[0143] 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. If precursors of the reducing gas are heated by gas heaters, waste heat from the gas heaters or steam generated by such heat sources can also be used.
[0144] 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 implementing a method according to the invention. A further subject matter is a signal processing device for implementing a method according to one of claims 1 to 8.
[0145] 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 commands for a signal processing device that, upon execution of the program for the signal processing device, 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 a schematic of another variant. Figure 3 shows another variant.
[0151] Figure 4 shows schematically another variant.
[0152] Description of the embodiments
[0153] Examples
[0154] Figure 1 schematically shows a device 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.
[0155] For this purpose, a first gas stream containing ammonia is subjected to ammonia cracking, producing a cracking gas stream. For this purpose, the ammonia-containing first gas stream is fed via a first gas stream line 50 to an ammonia cracking device 60, where at least a portion of the ammonia in the ammonia-containing gas stream is cracked. A second gas stream containing carbon is subjected to reforming, producing a reforming gas stream. For this purpose, the carbon-containing second gas stream is fed via a second gas stream line 70 to a reforming device 80, where reforming takes place.
[0156] In the ammonia cracking device 60, ammonia-crackable 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 ammonia-containing gas is cracked in the ammonia cracking device 60, producing cracking gas. A cracking gas flow line 61 extends from the ammonia cracking device 60.
[0157] Reforming conditions prevail in the reforming device 80 at a temperature in a range with a lower limit of 700°C and an upper limit of 1150°C, preferably 1000°C. At least a portion of the carbon-containing gas is reformed in the reforming device 80. Reforming gas is obtained in the reforming device 80. A reforming gas stream line 81 extends from the reforming device 80. The cracking gas stream line 61 and the reforming gas stream line 81 open into a combining gas stream line 90, thus allowing the combining of at least a portion of the cracking gas stream and at least a portion of the reforming gas stream, which can occur during the extraction of the reducing gas. The combining gas stream line 90 can include a gas mixer section; however, this is not shown separately for clarity. The combining gas stream line 81 opens into the reducing gas inlet 40.
[0158] Heat generated during reforming is supplied to the ammonia cracking process. For this purpose, a heat supply device 100—illustrated as a wavy line between the reforming device 80 and the ammonia cracking device 60—is provided to supply heat generated during reforming in the reforming device 80 to the ammonia cracking device 60. The heat supply device 100 can be a heat exchanger for exchanging heat with flue gas from the reforming device.
[0159] In the first gas flow line for ammonia-containing gas 60, a heating device for heating the ammonia may be present, but this is not shown separately for the sake of clarity.
[0160] In the second gas flow line for carbon-containing gas 50, a heating device for heating the carbon-containing gas can be present, but this is not shown separately for the sake of clarity.
[0161] The ammonia cracking device 60 can optionally comprise an electric heating device 101; the optionally present electric heating device 101 is schematically represented by a lightning bolt. A heating device can also optionally 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, or waste heat from gas heaters for heating, although this is not shown separately for clarity.
[0162] The ammonia cracking device 60 can optionally comprise an electric heating device 101; the optionally present electric heating device 101 is schematically represented by a lightning bolt. A heating device can also optionally 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, or waste heat from gas heaters for heating, although this is not shown separately for clarity.
[0163] The reforming device 80 may optionally include an electric heating device 102. An electric heating device heats using electrical energy.
[0164] 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, or waste heat from gas heaters, which, however, is not shown separately for the sake of clarity.
[0165] The fission gas flow line 61 can optionally contain a heating device for heating the fission gas flow, which is not shown separately for the sake of clarity.
[0166] The reforming gas stream line 81 may optionally contain a heating device for heating the cracking gas stream, which is not shown separately for the sake of clarity.
[0167] A heating device for heating the combining gas flow line 90 can optionally be present in the combining gas flow line, but this is not shown separately for the sake of clarity.
[0168] There is no device for reducing the ammonia content in the combination gas flow line 90.
[0169] 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 60.
[0170] In Figure 1, the ammonia cracking device 60 is embodied as an ammonia cracker separate from the reforming device 80. Figure 2 shows a design largely identical to Figure 1, but differing in the design of the ammonia cracking device 60. Schematically shown is an embodiment of the ammonia cracking device 60 integrated into parts of the reforming device 80. The ammonia cracking device 60 comprises tubes containing catalyst material for ammonia cracking; a tube 62 is shown.
[0171] The ammonia splitting device 60 is integrated into parts of the reforming device 80.
[0172] The reforming device 80 is a reformer comprising a plurality of tubes (not shown) containing catalyst material for reforming within a housing 82. The ammonia cracking device 60 is integrated into parts of the reforming device 80 by arranging tubes 62 containing catalyst material for ammonia cracking within the housing 82. When burners are used to supply heat for reforming, flue gas is produced from the combustion processes. This exhaust gas from the reforming process can flow around the tubes 62 containing catalyst material for ammonia cracking of the ammonia cracking device 60, which are arranged in the housing 82, and thereby supply heat to the ammonia cracking device 60.
[0173] Figure 3 shows a design largely identical to Figure 1. Additionally, a variant is shown in which a top gas outlet 110 is provided for discharging top gas from the reduction unit 30. The top gas outlet 110 flows into the second gas flow line for carbon-containing gas 70. Also shown is an optional—and therefore shown in dashed lines—treatment device 120, in this case a dust removal device. The top gas outlet 110 does not contain a device for reducing the carbon dioxide content.
[0174] The top gas outlet 110 may contain a device for separating nitrogen N2, although this is not shown separately for clarity. A fuel line for supplying top gas as a fuel component for burners of the reforming device 80 may extend from the top gas outlet, although this is not shown separately for clarity.
[0175] Figure 4 shows a design largely identical to Figure 1. The additional features shown will now be discussed:
[0176] - The device 10 for reducing metal oxide-containing material 20 also includes a device for controlling and / or regulating 130 the quantitative ratios of ammonia and hydrogen in the reducing gas. Also shown is its sensor 140 for determining the ammonia and hydrogen content in the reducing gas. - The device 10 for reducing metal oxide-containing material 20 also includes a hydrogen addition line 150 for adding hydrogen H2 to the combining gas flow line 90. The hydrogen addition line 150 opens into the combining gas flow line 90.
[0177] - the device 10 for reducing metal oxide-containing material 20 also comprises an ammonia addition line 160 for adding ammonia to the combining gas flow line 90. The ammonia addition line 160 opens into the combining gas flow line 90.
[0178] - the device 10 for reducing metal oxide-containing material 20 also comprises an ammonia supply line 170 for adding ammonia to the reduction unit 30. The ammonia supply line 170 opens into the reduction unit 30 and is independent of the introduction of the reducing gas into the reduction unit 30.
[0179] A heating device for heating the ammonia can be present in the ammonia supply line 170; for example, a heat exchanger, for example, for heat exchange with exhaust gas from the reforming process. To utilize the waste heat from the reforming process, line sections in a heat exchanger can be used, for example, which can also be used for heating top gas fuel by heat exchange with waste heat from the reformer.
[0180] Also usable are 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 waste heat from gas heaters, or steam generated using such heat sources. However, these are not shown separately for clarity.
[0181] 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 waste heat from gas heaters, or steam generated by such heat sources. However, this is not shown separately for clarity. List of reference symbols
[0182] 10 Device for reduction
[0183] 20 metal oxide-containing material
[0184] 30 Reduction unit
[0185] 40 Reducing gas introduction
[0186] 50 first gas flow line (for ammonia-containing gas)
[0187] 60 Device for ammonia splitting
[0188] 61 Fission gas flow line
[0189] 62 tube (containing catalyst material for ammonia decomposition)
[0190] 70 second gas flow line (for carbon-containing gas)
[0191] 80 Reforming device
[0192] 81 Reforming gas flow line
[0193] 82 Enclosure
[0194] 90 Union gas flow line
[0195] 100 heat supply device
[0196] 101 electric heating device
[0197] 102 electric heating device
[0198] 110 Top gas discharge
[0199] 120 processing device
[0200] 130 Device for controlling and / or regulating the proportions (of ammonia and hydrogen in the reducing gas)
[0201] 140 sensors
[0202] 150 Hydrogen addition line
[0203] 160 Ammonia addition line
[0204] 170 Ammonia supply line
Claims
1. A method for reducing a material containing a metal oxide, which uses a reducing gas obtained using ammonia NH3 and a carbon-containing gas by introducing it into a reduction unit, wherein, when obtaining the reducing gas, a first gas stream containing ammonia is subjected to ammonia cracking, resulting in the formation of a cracking gas stream, and a second gas stream containing carbon is subjected to reforming, resulting in the formation of a reforming gas stream, and combining at least a portion of the cracking gas stream and at least a portion of the reforming gas stream, and this combined gas stream obtained as a result of combining contributes to the formation of a reducing gas, characterized in that the heat released in the reforming process is fed to the ammonia cracking process, wherein the reforming is performed as steam reforming and / or as CO2 reforming.
2. The method according to claim 1, wherein a flue gas is formed in the reforming process, characterized in that the heat supplied to the ammonia cracking process is at least partially provided by the flue gas.
3. The method according to any one of paragraphs 1, 2, 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.
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 nitrogen content is reduced during the treatment process.
5. The method according to any one of paragraphs 1-4, characterized in that ammonia is added to the combined gas stream when obtaining the reducing gas.
6. The method according to any one of paragraphs 1-5, in which the reduction of the material containing the metal oxide is carried out in a reduction unit (30), characterized in that in addition to introducing the reducing gas into the reduction unit (30), ammonia is added.
7. The method according to any one of claims 1 to 6, characterized in that the concentration of NH3 in the reducing gas does not exceed 10 vol.%, preferably does not exceed 8 vol.%, in particular, preferably does not exceed 6 vol.%.
8. The method according to any one of paragraphs 1-7, characterized in that the ammonia content in the cracking gas stream, or in the portion of the cracking gas stream intended for combination with at least a portion of the reforming gas stream, is not reduced.
9. A device (10) for reducing a material containing a metal oxide, comprising: - recovery unit (30), - pipeline (40) for reducing gas entering the reduction unit (30), - the first pipeline (50) for gas containing ammonia, - the second pipeline (70) for carbon-containing gas, - a device (60) for cracking ammonia, - reforming device (80), - pipeline (61) for the flow of cracking gas, - pipeline (81) for reforming gas flow, - pipeline (90) for the combined gas flow, wherein the first pipeline (50) enters the device (60) for cracking ammonia, and the second pipeline (70) enters the device (80) for reforming, and the pipeline (61) for the cracking gas stream departs from the device (60) for cracking ammonia, wherein the pipeline (81) for the reforming gas stream departs from the device (80) for reforming, wherein the pipeline (61) for the cracking gas stream and the pipeline (81) for the reforming gas stream enter the pipeline (90) for the combined gas stream, and the pipeline (90) for the combined gas stream has an input into the pipeline (40) for reducing gas, characterized in that a heat supply device (100) is provided, intended for supplying heat released during the reforming process in the device (80) for reforming to the device (60) for cracking ammonia, wherein the reforming is steam reforming and / or as CO2 reforming.
10. The device according to item 9, characterized in that in the pipeline (61) for the flow of cracking gas there is no device for reducing the ammonia content.
11. The device according to claim 9 or 10, characterized in that in the direction of gas flow to the recovery unit (30) after the device (60) for cracking ammonia there is no device for reducing the ammonia content.
12. A device according to any one of paragraphs 9-11 with an upper gas outlet (110) for removing exhaust gas from the recovery unit (30), characterized in that the upper gas outlet (110) does not contain a device for reducing the carbon dioxide content.
13. A device according to any one of paragraphs 9-12 with an upper gas outlet (110) for removing exhaust gas from the recovery unit (30), characterized in that the upper gas outlet (110) contains at least one device for separating nitrogen N2.
14. The device according to any one of paragraphs 9-13, characterized in that it comprises at least one ammonia supply line (160) for adding ammonia to the pipeline (90) for the combined gas flow.
15. The device according to any one of paragraphs 9-14, characterized in that it contains at least one ammonia supply line (170) for adding ammonia to the recovery unit (30).