Ammonia as a reducing agent in steel production

Abstract

Disclosed is a method for producing steel, ferrous alloys or pig iron, and a melting furnace installation, which use ammonia.

Description

[0001] Page 1 / 21

[0002] Applicant: SMS group GmbH

[0003] Our reference number: P81096DE

[0004] November 20, 2024

[0005] Ammonia as a reducing agent in steel production

[0006] Large quantities of green hydrogen are needed to decarbonize the metal industry. However, it cannot be produced cost-effectively and in sufficient quantities in all regions where it is required. The global transport of green hydrogen is therefore crucial and simultaneously presents a challenge. Since transporting pure hydrogen is only possible as a gas under very high pressures exceeding 200 bar or as a liquid at very low temperatures below -252 °C, it is highly inefficient. A promising alternative is its conversion to ammonia as a hydrogen carrier. Ammonia can be liquefied at temperatures as low as -33 °C and is therefore easier to transport and store. Furthermore, ammonia has a higher volumetric hydrogen density, allowing larger quantities of hydrogen to be transported and stored within the same volume.

[0007] Currently, ammonia crackers are used to release hydrogen from ammonia, splitting it into hydrogen and nitrogen. This process occurs catalytically at temperatures of 600–900°C. Ammonia decomposition therefore requires a separate reactor and is also energy-intensive. Direct use of ammonia in metallurgical processes is thus preferable to upstream decomposition in a separate apparatus. Page 2 / 21

[0008] P81096DE

[0009] The invention relates to a process with the direct use of ammonia for the production of steel, ferroalloys or pig iron and a suitably appropriate plant.

[0010] The invention is based on the objective of providing a new process and a novel smelting furnace plant by which steel, ferroalloys or pig iron can be produced by the direct use of ammonia as a reducing agent.

[0011] The problems underlying the invention are solved by a method with the features of claim 1. Advantageous embodiments are described in the dependent claims.

[0012] More precisely, the problem underlying the invention is solved by a method for producing steel, ferroalloys or pig iron, comprising the steps of:

[0013] - Providing a smelting furnace plant with at least one electrode and / or induction coil for electrical energy input, wherein an iron molten metal and / or slag is present in the reactor space of the smelting furnace plant, obtained from at least one feedstock;

[0014] - Introducing an ammonia (NH3)-containing first gas into the iron molten metal and / or slag via a gas introduction device;

[0015] - At least partial conversion of the first gas to a second gas with increased nitrogen and hydrogen content, which has a reducing effect towards metal oxides; and

[0016] - Obtaining steel, ferroalloys or pig iron.

[0017] Advantageously, ammonia can be injected directly into the slag and / or the molten metal in the smelting plant. Page 3 / 21

[0018] P81096DE Ammonia, which partially converts to hydrogen, acts as a reducing agent to reduce the metal oxides present.

[0019] Since the temperatures in the molten metal are sufficient to split ammonia into hydrogen and nitrogen, the use of additional auxiliary materials such as catalysts is also unnecessary.

[0020] The ammonia-containing first gas may contain CH4, CO, CO2, H2, N2, and / or H2O. To ensure a reducing effect of the first gas, the total proportion of NH3, CO, CH4, and H2 can be at least 50%, 60%, 70%, 80%, 90%, 95%, or 99% v / v. A proportion between 85% and 95% v / v is preferred. Traces of longer-chain hydrocarbons, carbon nitrogen, and nitrogen oxides may also be present.

[0021] At least one of the starting materials can be an unreduced and / or partially reduced metal oxide.

[0022] In particular, the feedstock can be iron ore, partially reduced iron ore, direct reduced iron, hot briquetted iron or a mixture of the aforementioned feedstocks.

[0023] For example, the raw material can have a medium metallization level of 50%-100%, or 60%-95%.

[0024] Therefore, it is advantageously possible to use incompletely reduced material alone or as a subset with this method.

[0025] The energy input can be controlled by the electrode and / or induction coil and / or the quantity and / or inlet temperature of the first gas. Page 4 / 21

[0026] P81096DE

[0027] Gas can be introduced completely or in portions, either through a hollow electrode or via a separate gas introduction device. If the gas introduction device is a lance, the reaction process can also be controlled by the position of the lance's outlet within the reactor chamber.

[0028] The lance is movable at least vertically, thus allowing control of the vertical position of the lance outlet within the reactor chamber. This, in turn, allows control over the height at which the first gas escapes within the molten rock or slag.

[0029] By simultaneously controlling at least two of the aforementioned factors, or additional factors, the ammonia decomposition or metallurgy process can be monitored via suitable sensors and controlled by actuators. Suitable model- or data-driven algorithms (with and without the use of AI) can be employed to optimize process control.

[0030] The first gas can have a temperature of 25 °C (ambient or room temperature up to 1700 °C, preferably 400 °C to 800 °C) when introduced at the inlet of the gas introduction device.

[0031] In principle, the first gas can be introduced at room temperature, and heating it to the desired reaction temperature can take place in the reactor chamber. However, it may also be desirable to preheat the first gas to a temperature above room temperature in order to optimize the ammonia decomposition process.

[0032] The temperature in the molten metal during operation can be 1000–1700°C, 1300–1700°C, or 1450–1700°C. Page 5 / 21

[0033] P81096DE

[0034] The gas supply for the gas inlet device is located outside the reactor compartment. This means that the point of entry for the first gas is separated from the reactor compartment.

[0035] The second gas may contain a ratio in vol. -% of (H2+ CO ) to (H2O + CO2) greater than 10 , 30 , 50 , 70 or 90 .

[0036] The first gas can be conditioned in terms of composition, temperature, and / or pressure before being introduced. Thus, the first gas can have a pressure between 1 bar and 50 bar or 1 bar and 20 bar at the inlet of the gas introduction device.

[0037] Thus, the reaction conditions for ammonia decomposition and metallurgy can be optimized.

[0038] The second gas may include free hydrogen, and the process may further include the following step: reacting the free hydrogen with oxygen within the melting furnace.

[0039] The oxygen can be dissolved oxygen in the melt, an oxide slag component and / or a solid oxide.

[0040] The process may also include at least partial extraction of gas from the reactor space and at least one of the following steps:

[0041] - Removal or partial removal of the non-reducing or inert components from the extracted gas, and / or

[0042] - Extracting the reducing gas components from the extracted gas, and / or

[0043] - Use of the reducing gas components in a further process. Page 6 / 21

[0044] P81096DE

[0045] The non-reducing or inert components of the gases removed from the reactor space can be CO2, H2O, and / or N2.

[0046] The reducing gas components can be CO, H2, NH3, hydrocarbons.

[0047] In the further process, the reducing gas components can be used as reducing agents or energy carriers.

[0048] This makes it advantageously possible to use even the gaseous byproducts in further processes.

[0049] Furthermore, a smelting furnace plant for the production of steel, ferroalloys or pig iron is shown, comprising:

[0050] - a reactor room set up to provide molten iron and / or slag from a feedstock;

[0051] - at least one electrode and / or induction coil for introducing energy into the reactor space;

[0052] - at least one gas injection device set up for introducing NH3-containing gas into the iron molten metal and / or slag ,

[0053] - whereby the (air) oxygen leakage into the reactor space of the melting furnace plant is largely prevented by suitable design measures,

[0054] - characterized by the fact that

[0055] - the melting furnace plant is set up to at least partially convert the NH3-containing gas to a second gas, wherein the at least second gas has a reducing effect towards metal oxides .

[0056] Such a melting furnace plant is set up to carry out the procedures described above. Page 7 / 21

[0057] P81096DE

[0058] Such a melting furnace plant has the advantage that ammonia can be converted directly into reducing gases at the point of need without any further intermediate stage.

[0059] Such a smelting plant can be based, for example, on an induction furnace (IF), submerged arc furnace (SAF), oak bath furnace (OBF), or electric arc furnace (EAF). The smelting furnace plant described here differs from prior art SAFs, OBFs, and EAFs primarily in that it includes a gas injection device for introducing NH3-containing gas into the iron melt and / or slag, thus enabling ammonia decomposition.

[0060] The electrode and / or induction coil are not specifically limited.

[0061] Any electrically operated device suitable for introducing thermal energy into the reactor chamber is suitable. A combination with additional burners for energy input is possible.

[0062] Depending on the design, the electrodes can be operated with alternating current or direct current and are guided through the furnace lid and arranged in the reactor chamber and / or in the reactor wall or reactor floor.

[0063] An alternating current-powered induction coil (n) surrounds the reactor space and can induce current in metal-containing material within the reactor space.

[0064] The gas injection device, at least one of which can be designed in different ways, is possible. A combination of different gas injection designs is also conceivable. Page 8 / 21

[0065] P81096DE

[0066] The at least one gas injection device can be designed as a hollow electrode.

[0067] At least one gas injection device can be a lance.

[0068] The lance protrudes into the reactor chamber and can be designed to be movable.

[0069] Movable means that the lance outlet can allow the first gas to flow out at different heights within the reactor chamber (and thus at different heights within the material). The lance outlet is located inside the reactor chamber, and the inlet is outside the reactor chamber and at a distance from it.

[0070] At least one lance can be equipped with a gas-permeable outlet device. This gas-permeable outlet device ensures a fine distribution of the initial gas flow.

[0071] The lance can be inserted into the reactor space from above, e.g. through a lid that limits the reactor space at the top.

[0072] There can be 1, 2, or more lances.

[0073] Additionally or alternatively, a gas injection device may have one or at least one purge stone. The at least one purge stone may be embedded in the floor of the reactor chamber and / or in the side wall, e.g., in a lower section of the side wall of the reactor chamber.

[0074] This allows the first gas to be introduced into the molten metal from below. Page 9 / 21

[0075] P81096DE

[0076] There may be 1, 2, or more sink stones.

[0077] The flushing stones can be arranged in circular lines around the longitudinal axis of the reactor room in the reactor floor and / or the reactor room wall, and can be evenly distributed.

[0078] This allows for a preferentially evenly distributed inflow of the first gas.

[0079] The melting furnace system can be set up in various ways to prevent oxygen from entering the reactor space.

[0080] The melting furnace system can, for example, have a closed reactor room or be designed in such a way that substances are introduced into or removed from the reactor room via locks.

[0081] The enclosed reactor space prevents unwanted air from entering the reactor space.

[0082] Alternatively or additionally, the melting plant may have a barrier device to reduce or prevent oxygen from entering the reactor chamber.

[0083] For example, the inflow of the first gas can be controlled in such a way that there is an overpressure above the melt or slag that is higher than the atmospheric pressure outside the reactor space.

[0084] The melting furnace system may also have a gas outlet through which gas can be extracted from the reactor room.

[0085] Also revealed is a melting furnace system comprising at least one melting furnace system as described above, page 10 / 21

[0086] P81096DE and other devices and systems for introducing feedstocks, control devices for electrodes and / or induction coils, devices and systems for providing the initial gas or for extracting and processing the gas extracted from the reactor space, such as a gas processing plant, optionally a hot gas filter, and / or a reduction plant.

[0087] The melting furnace plant or melting furnace system can be set up to carry out the procedure described above.

[0088] The melting furnace plant or melting furnace system may further have the following features: a. measuring sensors for process parameter acquisition; b. a computer-based control system i. for acquiring and processing the measurement data transmitted by the measuring sensors; and ii. for controlling iii. the electrode and / or induction coil, iv. the quantity and / or composition and / or temperature and / or pressure of the introduced first gas, and / or v. the quantity and / or composition of the at least one introduced feedstock, and / or vi. the composition and quantity of the steel, ferroalloy, or pig iron obtained; and / or vii. the composition, temperature, and / or quantity of the second gas obtained; wherein the control is based on the acquired and processed measurement data. Page 11 / 21

[0089] P81096DE

[0090] In this way, semi-automatic or fully automatic control or regulation of the melting furnace plant or melting furnace system is possible.

[0091] The computer system can be configured to carry out the above-described procedure in the melting furnace system. Suitable model- or data-driven algorithms (with and without the use of AI) can be incorporated into the computer system to optimize process control.

[0092] Further advantages, details and features of the invention will become apparent from the exemplary embodiments described below.

[0093] Specifically, they show:

[0094] Fig. 1 schematically shows the structure of a melting furnace system.

[0095] Fig. 2 schematically shows the structure of a melting furnace system during its operation.

[0096] In the following description, identical reference numerals denote identical components or identical features, so that a description given for a component in relation to one figure also applies to the other figures, thus avoiding repetitive descriptions. Furthermore, individual features described in connection with one embodiment can also be used separately in other embodiments.

[0097] Fig. 1 schematically shows an example of a melting furnace 1 disclosed herein without loading.

[0098] The melting furnace unit 1 has an electrode or electrode group 2 that protrudes from the lid of the melting furnace unit. In the case of a direct current version, there are also electrodes in the reactor wall (page 12 / 21).

[0099] P81096DE and / or electrodes in the reactor base. Alternatively, an induction coil can be provided around the reactor chamber.

[0100] The melting furnace 1 has at least one gas introduction device 3. The first gas, the ammonia-containing gas, is introduced via this device.

[0101] The electrode 2 can be a hollow electrode 2 and thus also be designed as a gas introduction device through which the first gas, the ammonia-containing gas, can be introduced.

[0102] The gas introduction device 3 can be a lance 3a. This lance 3a can enter the reactor chamber through the cover of the reactor chamber as shown here.

[0103] The gas introduction device 3 can also be at least one flushing stone 3a, 3b. Flushing stones 3a, 3b can be provided in the floor of the reactor chamber, as shown here.

[0104] Lances 3a, hollow electrode 2 and flushing stones 3a, 3b can be used in combination, but can also each be used individually.

[0105] The smelting furnace plant 1 also has at least one outlet 4 for steel, ferroalloys or pig iron and / or slag.

[0106] There may also be separate outlets 4 for steel, ferroalloys or pig iron on the one hand and slag on the other.

[0107] Furthermore, the melting furnace 1 has a filling device 6 for feedstocks, such as unreduced and / or partially reduced metal oxide, e.g. iron ore, a Direct Reduced Iron, Hot Page 13 / 21

[0108] P81096DE

[0109] Briquetted iron and / or other additives, which are conveniently connected in the upper part of the melting furnace system (e.g. the lid).

[0110] In the upper part of the melting furnace system 1 (e.g., the lid), a gas outlet 7 is also provided, through which gas can be extracted. The extracted gas can be nitrogen, water, carbon monoxide, carbon dioxide, hydrocarbons (C x H y) , ammonia and / or gaseous hydrogen.

[0111] The melting furnace system 1 of Fig. 1 has a closed reactor chamber 1a, so that the ingress of air and oxygen into the reactor chamber 1a is reduced or prevented. Therefore, the respective inlet and outlet lines can contain airlocks.

[0112] Alternatively or additionally, a barrier device can be provided to reduce or prevent the ingress of air and oxygen into the reactor chamber. For example, overpressure can be created in the reactor chamber using an oxygen-free gas, e.g., via a pumping device.

[0113] Figure 2 illustrates the melting furnace system 1 from Fig. 1 with filling, i.e. during operation.

[0114] The metal melt 7 is located in the lower part of the reactor room.

[0115] This molten metal 7 can be withdrawn via the outlet 4. A first gas containing ammonia can be introduced into the reactor chamber via the at least one gas introduction device 3 within the molten metal 7.

[0116] Above the molten metal 7, the slag 8 is located during operation. Page 14 / 21

[0117] P81096DE

[0118] This slag 8 can be removed via outlet 4 after the removal of the molten metal (lowering of the metal liquid level).

[0119] A closed, electrically operated melting furnace 1 of type OBF / SAF / EAF containing pig iron as the molten metal 7, possibly also with slag 8 on top, can be used, into which the first ammonia-containing gas is injected via lance 3a. The injection preferably takes place into the molten metal 7.

[0120] The ammonia from the first gas is decomposed endothermically in the molten metal 7. Nitrogen and hydrogen are produced (2 NH3 → N2 + 3 H2).

[0121] The hydrogen formed by the decomposition of ammonia is heated in the molten metal 7 and acts in the reactor as a reducing agent towards oxygen present, e.g. in oxides in the slag 8, and / or towards solid oxides (Fe x O y + yH2 x Fe + y H2O) .

[0122] The excess gas rises in the molten metal 7 and can be rich in hydrogen and possess a high reduction potential.

[0123] Therefore, this gas can be used, for example, in reduction plants (not shown).

[0124] Compared to a conventional direct reduction plant (based on methane), the process revealed here is therefore associated with fewer CO2 emissions.

[0125] The melting furnace system is therefore preferably operated as follows.

[0126] Scrap and / or partially or non-reduced material (e.g., DRI, HBI) is used as feedstock. Page 15 / 21

[0127] P81096DE

[0128] Reference symbol list

[0129] 1 Melting furnace system, reactor room 2 Electrode / Induction coil

[0130] 3 Gas introduction device

[0131] 3a Lance

[0132] 3b Sink

[0133] 4. Outlet for steel, ferroalloys or pig iron and / or outlet for slag

[0134] 5. Filling chute for ore and / or additives

[0135] 6 Gas outlet

[0136] 7 Metal melt

[0137] 8 Slag

Claims

Page 16 / 21 P81096DE Patent claims 1. A process for the production of steel, ferroalloys or pig iron, comprising the steps of: - Providing a melting furnace system with at least one electrode and / or induction coil for electrical energy input, wherein molten iron and / or slag is present in the reactor space of the melting furnace system, obtained from at least one feedstock; - Introducing an NH3-containing first gas into the iron melt and / or slag via a gas introduction device; - At least partial conversion of the first gas to a second gas with increased nitrogen and hydrogen content, which has a reducing effect towards metal oxides; and - Obtaining steel, ferroalloys or pig iron.

2. Method according to claim 1 wherein the NH3-containing first gas Includes proportions of CH4, CO, CO3, H2, N2 and / or H2O.

3. Method according to claims 1 and 2, wherein the at least one The feedstock is an unreduced, partially reduced metal oxide, iron ore, partially reduced iron ore, a direct reduced iron, hot briquetted iron or a mixture of the aforementioned feedstock materials with an average metallization degree of 50%-100%, or 60%-95%.

4. A method according to any one of the preceding claims, wherein the energy input is by means of an electrode and / or induction coil; and / or the quantity introduced and / or pressure and / or inlet temperature of the first gas; and / or wherein the gas introduction device is a hollow electrode or a lance. Page 17 / 21 P81096DE and the position of the gas outlet in the reactor room are controlled.

5. Method according to one of the preceding claims, wherein the first gas has a temperature of 25°C - 1700°C or 400°C - 800°C when introduced at the inlet of the gas introduction device and wherein optionally the inlet of the gas introduction device is arranged outside the reactor space.

6. Method according to one of the preceding claims, wherein the first gas has a pressure between 1 bar and 50 bar or between 1 bar and 20 bar when introduced at the inlet of the gas introduction device.

7. Method according to one of the preceding claims, wherein the second gas contains a ratio in vol.-% of (H2+ CO) and (H2O + CO2) greater than 10, 30, 50, 70 or 90.

8. Method according to any of the preceding claims, wherein the first gas is conditioned in composition and / or temperature and / or pressure before being introduced.

9. A method according to one of the preceding claims, wherein the second gas comprises free hydrogen, and the method further comprises: reacting the free hydrogen with oxygen within the melting furnace system, wherein optionally the oxygen is dissolved oxygen in the melt, an oxide slag fraction and / or a solid oxide.

10. Method according to one of the preceding claims, further comprising at least partial extraction of gas from the reactor space and at least one of the following steps: - Removal or partial removal of the non-reducing or inert components from the extracted gas, wherein Page 18 of 21 P81096DE optionally the non-reducing or inert components CO2, H2O, N2 are, - Extraction of the reducing gas components from the extracted gas, where optionally the reducing gas components are CO, H2, NH3, hydrocarbons, - Use of the reducing gas components in a further process, whereby optionally the reducing gas components are used as reducing agents or energy carriers in the further process.

11. Including a smelting furnace for the production of steel, ferroalloys or pig iron: - a reactor room set up to provide molten iron and / or slag from a feedstock; - at least one electrode, electrode group and / or induction coil for introducing energy into the reactor space; - at least one gas injection device set up for introducing NH3-containing gas into the iron molten metal and / or slag; - wherein the melting furnace system is designed to prevent oxygen from entering the reactor chamber, characterized in that - the melting furnace plant for at least partially converting the first gas to a second gas with increased nitrogen and hydrogen content, which has a reducing effect towards metal oxides.

12. Melting furnace system according to claim 11, wherein the at least one gas introduction device is either at least one hollow electrode and / or at least one lance which is optionally inserted from above into the reactor space, and / or has at least one purge stone, wherein optionally the at least one lance is equipped with a gas-permeable outlet device. - 18 - Page 19 / 21 P81096DE 13. Melting furnace system according to one of claims 11 - 12, wherein the at least one gas introduction device has at least one flushing stone, wherein the at least one flushing stone is arranged on the bottom and / or the wall of the reactor.

14. Melting furnace system according to one of claims 11 - 13, wherein the melting furnace system has a closed reactor space and / or a barrier device for reducing or preventing air oxygen from entering the reactor space.

15. Melting furnace system comprising at least one melting furnace system according to one of claims 11 - 14, a gas processing system, optionally a hot gas filter, and / or a reduction system.

16. Melting furnace plant according to one of claims 11-14 or melting furnace plant system according to claim 15, configured to carry out the method according to one of claims 1-10.

17. Melting furnace plant according to one of claims 11-14 or melting furnace plant system according to claim 15, further comprising - Measuring sensors for process parameter acquisition; - a computer-based control system - for recording and processing the measurement data transmitted by the measuring sensors; and - for control 1. the electrode and / or induction coil, and / or 2. the quantity, pressure, temperature and / or composition of the first gas introduced, and / or - 19- Page 20 / 21 P81096DE 3. the quantity, temperature and / or composition of the at least one imported input material, and / or 4. the composition, temperature and quantity of the steel, ferroalloy or pig iron obtained; and / or 5. the composition, temperature and quantity of the second gas obtained; - wherein the control or regulation is based on the recorded and / or processed measurement data or derived therefrom Forecast data is available.

18. Melting furnace plant or melting furnace plant system according to claim 17, wherein the computer system is configured to carry out the method according to any one of claims 1-10 in the melting furnace plant.

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