How to operate a blast furnace plant

Abstract

A method of operating a shaft furnace plant is presented, comprising a shaft furnace and an ammonia reforming plant. The method comprises the steps of: (a.) providing an ammonia stream to the ammonia reforming plant; (b.) decomposing the ammonia stream in the ammonia reforming plant to produce a reducing gas stream; (c.) providing a metal oxide-containing input, e.g., an iron oxide-containing input, and a reducing gas stream to the shaft furnace; and (d.) reducing metal oxides in the shaft furnace by reaction with the metal oxide-containing input and the reducing gas stream, the reducing gas comprising less than 15% ammonia, preferably less than 10% ammonia. The invention also relates to a shaft furnace plant configured to carry out such a method.

Description

[Technical field]

[0001] The present invention relates generally to a method for operating a shaft furnace plant as well as to such a shaft furnace installation. In particular, the present invention relates to a method for operating a blast furnace plant or a plant including a direct reduction reactor. [Background technology]

[0002] The existence of the Paris Agreement and the near-global consensus on the need to act on emissions makes it essential for industry sectors to step up and develop solutions to improve energy efficiency and reduce CO2 emissions.

[0003] In this context, ferrous metallurgical actors have developed new approaches to reduce the environmental footprint of the blast furnace steelmaking route. Indeed, despite alternatives such as scrap melting or direct reduction in electric arc furnaces, the blast furnace (BF) still represents the most widely used process for iron and steelmaking today, and efforts have been made to reduce CO2 emissions from blast furnaces for many years, in order to contribute to the reduction of global CO2 emissions.

[0004] Coke is the main energy input in blast furnace steelmaking. From a CO2 point of view, and often also from an economic point of view, it is a less favourable energy source.

[0005] Strategies have been developed to recover blast furnace top gas from the blast furnace, treat it to improve its reduction potential, and inject it into the blast furnace to aid the reduction process, primarily to reduce coke consumption. One way to do this is to reduce the CO2 content in the blast furnace gas by pressure swing adsorption (PSA) or vacuum pressure swing adsorption (VPSA). The PSA / VPSA system produces a first gas stream rich in CO and H2 and a second gas stream rich in CO2 and H2O. The first gas stream is used as reducing gas and is pumped back into the blast furnace. The PSA / VPSA system can reduce the CO2 content in the blast furnace gas from about 40 mol-% to about 5 mol-%, but it is very expensive to acquire, maintain and operate, and requires a lot of space.

[0006] Considerable efforts are also being made to reduce the use of carbonaceous fuels for the operation of the blast furnace itself, with a view to reducing CO2 emissions. The replacement of coke with other energy sources, mainly injected at the tuyere level, is now widely adopted. For cost reasons, mainly pulverized coal is injected. Additionally or alternatively, fuels with increased hydrogen content in the form of hydrocarbons, gaseous hydrogen H2, or mixtures thereof are used, mainly in countries where the price of natural gas is low. Due to their high calorific value, hydrogen and hydrocarbons have the potential to be injected into the tuyere of the blast furnace as supplementary fuels.

[0007] These auxiliary fuels have a positive impact on CO2 emissions from blast furnace steelmaking, but their use is limited for process reasons, and today in many cases these limits are already reached. Indeed, the higher the hydrogen participation, the higher the CO2 reduction potential of blast furnace operation in general. However, the injection of cold H2 and / or hydrocarbons through the tuyere together with large amounts of pulverized coal (PCI) significantly reduces the RAFT (raceway adiabatic flame temperature). To increase the RAFT, a higher oxygen enrichment is required, which is limited by the top gas temperature. Therefore, only relatively small amounts of cold H2 and / or hydrocarbons can be injected into the blast furnace through the tuyere, limiting the CO2 saving potential of this technology.

[0008] Furthermore, in some countries, sufficient green energy is not available to meet the needs of steel plants. Also, producing and / or importing hydrogen is very costly and difficult, and requires specific infrastructure. Therefore, there remains a need for alternative ways to supply hydrogen-enriched gas to shaft furnaces, especially blast furnaces. Summary of the Invention [Problem to be solved by the invention]

[0009] It is therefore an object of the present invention to provide a method for operating a shaft furnace plant as well as a corresponding shaft furnace plant, which reduces the CO2 emissions resulting from the operation of the shaft furnace and at least partially overcomes the above-mentioned problems.

[0010] This object is achieved by a method according to claim 1 and by a shaft furnace plant according to claim 15. [Means for solving the problem]

[0011] In order to achieve the above object, the present invention proposes, in a first aspect, a method for operating a shaft furnace plant including a shaft furnace and an ammonia reforming plant, the method comprising: a. providing an ammonia stream to an ammonia reforming plant; b. Cracking the ammonia stream in an ammonia reforming plant to produce reducing gas; c. feeding a metal oxide containing charge to a shaft furnace; d. reducing the metal oxide in the shaft furnace by reacting the metal oxide charge with a reducing gas.

[0012] According to the invention the reducing gas contains less than 15 mol-% ammonia, preferably less than 10 mol-% ammonia. The shaft furnace is preferably used to produce iron (from an iron oxide containing charge), e.g. pig iron, slag, direct reduced iron (sponge iron), hot briquetted iron (HBI), etc., although the process can be applied to produce other metals, such as lead or copper, from corresponding metal oxide containing charges.

[0013] The method is particularly adapted to preferred embodiments in which the shaft furnace is either a direct reduction reactor or a blast furnace, however, the method can be implemented to operate a shaft furnace plant including any type of shaft furnace.

[0014] In the context of this disclosure, reducing gas refers to a gas capable of reducing metal / iron oxide-containing inputs during oxidation, thereby producing metal / iron. In this context, ammonia decomposition may be referred to as ammonia reforming, reducing gas may also be referred to as cracked ammonia, and unreacted ammonia may be referred to as undecomposed ammonia or unreformed ammonia.

[0015] In the context of this disclosure, iron oxide-containing input refers to materials that contain iron oxides and / or mixed oxides of iron(II) and iron(III), such as iron hydroxides, iron oxide-hydroxides, and oxides of iron(II) or iron(III). Iron oxide-containing input may refer to iron ores from which metallic iron can be economically extracted. Such iron ores are typically rich in iron oxide in the form of magnetite (Fe3O4, 72.4 wt.-% Fe), hematite (Fe2O3, 69.9 wt.-% Fe), goethite (FeO(OH), 62.9 wt.-% Fe), limonite (FeO(OH)·n(H2O), 55 wt.-% Fe), or siderite (FeCO3, 48.2 wt.-% Fe). The iron oxide-containing input may also include direct reduced iron (sponge iron (DRI)), hot briquetted iron (HBI), scrap, or mixtures thereof.

[0016] In the context of this disclosure, a reforming plant is an ammonia reforming plant (also called an ammonia cracking plant) and includes at least one reformer configured to reform (i.e., crack) ammonia according to the following reaction: 2NH3→N2+3H2 In other words, the reforming plant is where the ammonia is cracked.

[0017] In an embodiment, other reducing agents and / or carburization agents and / or fuel and reducing gas or mixtures thereof are fed into the shaft furnace.

[0018] In the context of this disclosure, and when the shaft furnace is a blast furnace, typical reducing and carburizing agents are materials injected at the tuyere of the blast furnace, such as pulverized coal, natural gas, coke oven gas, biogas, syngas, charcoal... and coke that charges at the top of the blast furnace along with the iron-bearing material.

[0019] In the context of this disclosure, and in the case of direct reduction furnaces, typical reducing and carburizing agents are natural gas and syngas (gases produced from the reforming of hydrocarbon-containing gases such as natural gas, containing primarily CO, H2 and smaller amounts of CH4, N2, H2O, CO2...).

[0020] In an embodiment, the ammonia reforming plant may include multiple reformers arranged in series or parallel with each other, or the ammonia reforming plant may include multiple reformers arranged to form at least two series of reformers arranged in parallel with each other. In an embodiment where the ammonia reforming plant includes multiple reformers, the reformers may be identical or different from each other. The exact number, type and arrangement of the reformers in the ammonia reforming plant may be advantageously adapted depending on the subsequent feeding of the produced reducing gas to the shaft furnace to meet the requirements of the produced reducing gas (e.g. temperature, residual amount of ammonia, etc.).

[0021] In another aspect, the present invention also provides a method for producing a method for the treatment of a pulmonary arthritis, comprising: Shaft furnace; and Also proposed is a shaft furnace plant that includes an ammonia reforming plant with a gas inlet and a gas outlet, the gas inlet being fluidly connected to an ammonia source and / or a heat exchanger, and the gas outlet being fluidly connected to the shaft furnace.

[0022] The shaft furnace plant is advantageously adapted to be operated by carrying out the method according to the first aspect, as will be explained in more detail below.

[0023] Thus, the present disclosure proposes an integrated method and corresponding plants that allow the operation of shaft furnaces with reduced coke and / or other carbon sources, with low CO2 emissions and with optimal use of existing infrastructure.

[0024] The method proposes the use of ammonia as a novel, easy and economical energy carrier ideally applied to the steel industry and more specifically to the requirements of shaft furnaces, with the aim of reducing CO2 emissions whilst maintaining much of the existing infrastructure.

[0025] In fact, the inventors have found that this operating method fits very well with the CO2 lean energy strategies of various countries. The transportation of ammonia can be realized with equipment very similar to those dedicated to the transportation of liquefied natural gas (LNG) or liquefied petroleum gas (LPG), and since the liquefaction temperature of ammonia is -33°C at normal pressure, it can be relatively easily adapted to existing infrastructure. Thus, it is compatible with common LPG and / or LNG facilities.

[0026] To reduce the CO2 emissions of steel plants, ammonia can be used directly as additional fuel gas in burners such as hot stove plants, reheating furnaces... and burners in thermal power plants. When ammonia is used directly in burners, one faces the problem of NOx emissions associated with the combustion of nitrogen-rich ammonia fuel. Such problems are avoided when the decomposed hot ammonia is fed to the shaft furnace as a reducing agent (i.e., as reducing gas), as described above. The remaining reducing gas leaving the shaft furnace adds the components H2, H2O and N2 to the exiting top gas. When the H2O is condensed, the exiting top gas is enriched only in N2 and H2, and its impact on NOx formation during combustion is minimized. The exiting top gas also has the positive effect of increasing the lower calorific value, which leads to higher efficiency and therefore reduced energy consumption of downstream furnaces and thermal power plants using the top gas exiting from the shaft furnace.

[0027] Therefore, the main advantage of the proposed method is the identification of how to improve the efficiency of ammonia utilisation in steel plants, particularly in shaft furnaces, in order to further reduce CO2 emissions.

[0028] Another advantage is that the reforming (ie, cracking) process allows for the highly efficient production of synthesis gas with high hydrogen (H2) content from ammonia.

[0029] In addition, the decomposition of ammonia is a highly endothermic reaction and requires a great deal of energy to carry it out (i.e., approximately 2.5 MJ / Nm 3NH3). Injection of hot undecomposed ammonia into the shaft furnace is therefore thermally comparable to injection of cold N2 and cold H2 and therefore strongly reduces the temperature at the injection point, thereby slowing down the reaction of the reducing gas with the iron oxide-containing charge. To compensate for the cooling effect of the injection of undecomposed ammonia, more coke needs to be injected, which negatively impacts the potential for CO2 emission reduction. Decomposition of ammonia outside the shaft furnace therefore prevents the consumption of excess carbon-containing reducing agent during shaft furnace operation and allows a significant reduction in the CO2 emissions of the shaft furnace plant.

[0030] Furthermore, because the decomposition of ammonia takes place outside the shaft furnace, the reaction can be better monitored and controlled, allowing operators to always know the composition of the reducing gas supplied to the shaft furnace (i.e. the amount of H2 and N2, and potentially the amount of residual unreacted NH3), resulting in better control of iron production.

[0031] In an embodiment, the ammonia conversion in the ammonia reforming plant is constant over time, thereby ensuring that the reducing gas supplied to the shaft furnace exhibits the same reduction potential and therefore ensuring stable quality and characteristics of the reducing gas injected into the shaft furnace.

[0032] Alternatively, the reducibility and other properties (temperature, pressure, etc.) of the reducing gas are dynamically adapted to the changing requirements of the shaft furnace. Such adjustments are particularly important when the supply of iron oxide-containing input is not constant over time and / or when the quality of the iron produced needs to be adapted during production without stopping the shaft furnace.

[0033] The main advantages and effects of the operating method and shaft furnace installation according to the present disclosure can be summarized as follows: -Reuse of existing infrastructure; -Cost-effective transport compared to hydrogen transport as ammonia has a higher energy density on a volumetric basis than hydrogen; -Improved efficiency of ammonia utilization in shaft furnace operation.

[0034] These and further advantages of the method for operating a shaft furnace and the shaft furnace plant of the present disclosure are described in further detail below.

[0035] As mentioned above, the decomposition of ammonia occurs according to the following reaction: 2NH3 → N2 + 3H2 The use of a catalyst is useful because the decomposition (i.e., reforming) of ammonia requires a high activation energy. At high temperatures, i.e., typical temperatures required for injection in shaft furnaces, such as about 700°C to 1000°C, ammonia decomposition (i.e., cracking or reforming) can also be performed without the use of a catalyst. However, non-catalytic reforming of ammonia requires a long residence time of the ammonia in at least one reformer of the ammonia reforming plant, and therefore may require a larger reformer.

[0036] Thus, the reforming (ie, decomposition) of ammonia can be carried out catalytically or non-catalytically.

[0037] Additionally, the catalyst can be used to provide the endothermal heat required for the decomposition (i.e., reforming or cracking) of ammonia at low temperatures. This is all the more important since the decomposition (i.e., reforming) requires very high energy, similar to the energy required to heat ammonia from ambient temperature to about 1000° C. Thus, carrying out the reforming step at relatively low temperatures, i.e., below about 900° C., or even below about 700° C., helps to increase the thermal efficiency of the process. Thus, in embodiments, the decomposition of ammonia to produce a reducing gas stream in an ammonia reforming plant is catalytically favored.

[0038] Currently, the development of catalysts for ammonia decomposition (i.e. ammonia reforming) is still ongoing. Any type of catalyst can be used in the process, for example nickel-based catalysts or any catalyst that operates at high temperatures, i.e. up to about 1000° C. However, catalysts that operate near the expected thermodynamic temperature of about 500° C., where high ammonia conversion rates are obtained, can be advantageously used in the reformer to increase the thermal efficiency.

[0039] Advantageously, it is necessary to make the ammonia conversion as high as possible during the reforming process, since the higher the concentration of hydrogen H2 in the reducing gas, the lower the concentration of residual ammonia NH3. This is particularly important, since the decomposition of ammonia is endothermic, it cools the atmosphere in the shaft furnace and therefore has a negative effect on the processes in the shaft furnace. In fact, a reducing gas containing 10 mol % ammonia reduces its temperature by about 40 ° C when this ammonia is converted adiabatically.

[0040] Surprisingly, the inventors have found that when operating a shaft furnace plant in this manner, residual ammonia in the reducing gas is not an issue, since the resulting reducing gas needs to be at a high temperature, typically above 800° C., in order to inject it into the shaft furnace, nor is there a need for ammonia reforming (i.e. decomposition) at low temperatures.

[0041] As mentioned above, the reducing gas may contain ammonia, i.e. undecomposed (or unreformed) ammonia. The reducing gas may contain various levels of residual ammonia, such as less than 15 mol-% ammonia, less than 10 mol-% ammonia, or even less than 5 mol-% ammonia, depending on the requirements of the shaft furnace. Since the ammonia reforming process does not need to be complete, it is an easy quick win for efficient use of ammonia to reduce CO2 emissions in the shaft furnace.

[0042] The temperature of the reforming process, i.e. the temperature at which the decomposition of ammonia takes place, may preferably correspond substantially to the temperature at which the reducing gas is supplied to the shaft furnace.

[0043] The pressure of the reforming process, i.e. the pressure at which the cracking takes place, preferably corresponds to the pressure at the shaft level of the blast furnace, supplemented by pressure losses in the ducts and the reformer. The usual pressure level at the inlet of the reforming plant will be less than about 15 barg, more particularly less than 12 barg.

[0044] Advantageously, the ammonia reforming plant may include heat exchangers, such as room air conditioning, cooling water cooling, etc., arranged to supply cooling energy resulting from the heating, and possibly evaporation, of an ammonia stream provided from an ammonia store to at least one reformer to consumers within the steel plant.

[0045] Alternatively and / or additionally, the ammonia is heated in a heat exchanger before entering the reformer by flue gases originating from the ammonia reformer and / or flue gases originating from the combustion of a fuel gas used in particular for combustion purposes.

[0046] The heat exchanger can be of various types, such as tube bundle type, plate type heat exchanger, etc.

[0047] In a preferred embodiment, the method further comprises recovering a top gas stream from the shaft furnace and combusting the top gas stream in a burner of the ammonia reforming plant. In this context, top gas refers to gas exiting the top of the shaft furnace, e.g. blast furnace gas in embodiments where the shaft furnace is a blast furnace, and may also be referred to as shaft furnace gas. Alternatively or additionally, steel plant gas, ammonia itself and / or biofuels such as biogas, biomass... or mixtures thereof may be used in the burner of the ammonia reforming plant.

[0048] As mentioned above, a lot of energy is used in heating and decomposing (i.e., reforming) ammonia. It takes about 4.5 MJ / Nm to heat ammonia from gas to about 25°C to 950°C and reform (i.e., decompose) it into hydrogen H2 and nitrogen N2. 3 of ammonia NH3 is required. This energy can advantageously be provided by burning top gas from the shaft furnace in the burners of the ammonia reforming plant, making it possible, for metallurgical reasons, to directly recycle the energy of the shaft furnace gases to the shaft furnace instead of using it for the less energy-efficient production of electrical energy. Since no further combustion of carbonaceous fuel gases in the burners of the reforming plant is necessary, a further reduction in CO2 emissions can be achieved by the method of operating the shaft furnace plant. Alternatively or additionally, steel plant gases, ammonia itself and / or biofuels such as biogas, biomass... or mixtures thereof are used in the burners of the ammonia reforming plant.

[0049] According to a preferred embodiment, the supply of the reducing gas is directly through the shaft of the shaft furnace. In an embodiment where the shaft furnace is a direct reduction reactor, this means that the reducing gas is preferably injected into the reduction zone, and not into the throat or cooling zone of the reactor. In an embodiment where the shaft furnace is a blast furnace, this means that the reducing gas can be injected into the gas solid reduction zone of the ferrous oxide at shaft level, i.e. above the hot blast level, preferably above the cohesive zone. Injecting the produced reducing gas at the shaft level of the blast furnace allows a significant reduction in the coke rate, i.e. the amount of coke and / or other carbon sources per tonne of produced pig iron.

[0050] Alternatively or additionally, the reducing gas can be fed at the tuyere level of the blast furnace, preferably at a high temperature after decomposition. Although the injection of the reducing gas through the tuyere increases the oxygen required for the operation of the blast furnace, thereby generally reducing the possibility of supplementary fuel addition, the reducing gas containing the decomposed ammonia can be injected at the tuyere level at a high temperature after decomposition, with or without O2 addition to heat it up to flame temperature in the raceway, or with or without plasma heating outside the furnace already reaching flame temperature. Thus, the reducing gas containing the decomposed ammonia can be injected at the tuyere level, regardless of whether or not the (reducing) gas is injected at the lower shaft. Furthermore, the reducing gas containing the decomposed ammonia can be injected at the tuyere level, regardless of whether or not the top gas of the shaft furnace, previously heated directly and / or indirectly to 700-1000 ° C, recycled and cooled (condensed), is injected at the upper level of the shaft.

[0051] In a preferred embodiment, in addition to the reducing gas injected into the shaft of the blast furnace, an auxiliary fuel is fed into the blast furnace. The auxiliary fuel can advantageously be pulverized coal, natural gas, coke oven gas and / or hydrogen. The injection of reducing gas into the shaft furnace, in particular the shaft of the blast furnace, allows the injection of pulverized coal, natural gas, in particular also hydrogen, or other materials at higher tuyeres. In fact, the injection (or feeding) of cracked ammonia into the shaft as reducing gas increases the temperature of the top gas, which allows a higher oxygen enrichment at the tuyeres level, thus allowing the injection of higher auxiliary fuels such as PCI, NG, COG, hydrogen, etc. As mentioned above, ammonia containing cracked ammonia and / or reducing gas can also be added (as auxiliary fuel) at the tuyeres level, with or without O2 addition, with or without additional plasma heating, with or without injection of reducing gas at the lower shaft. In this way, the excess amount of coke can be replaced with hydrogen-rich auxiliary fuel, further reducing the carbon content of the blast furnace reductant (i.e. reducing the amount of coke required) and therefore reducing CO2 emissions.

[0052] In some embodiments, a synthesis gas stream is fed to the shaft furnace in addition to the reducing gas, in such embodiments, iron reduction is also produced by reaction between the synthesis gas stream and the iron oxide-containing input.

[0053] Synthesis gas streams may advantageously be produced by reforming industrial gases (e.g., shaft furnace top gas, steam and / or basic smelter gas, etc.) and fuel gases (e.g., coke oven gas, natural gas, methane and / or biogas, etc.).

[0054] According to the same or alternative embodiments, HBI and / or scrap may be fed to a blast furnace as part of the iron oxide-containing input.

[0055] HBI is an interesting form of energy transport since it combines ease of transport with a high energy density. In fact, existing infrastructure can be used to transport HBI, since its compact shape makes it easy to handle and transport. HBI is compressed direct reduced iron, i.e. pre-treated iron ore, and its transport advantageously combines the transport of raw materials fed as iron oxide-bearing inputs in blast furnaces with the transport of energy, while avoiding the transport of oxygen bound to the unreduced ore. In fact, since HBI is pre-treated iron ore, less energy is needed to obtain fully processed iron in the blast furnace, since HBI already has a high metallic iron content.

[0056] To achieve significant CO2 savings, HBI is preferably produced with green hydrogen, or alternatively, it can be produced from natural gas and carbon capture applied to the hydrogen and / or DRI production process.

[0057] The HBI fed to the blast furnace has the further advantage that a relatively low-grade ore can be used for its production. This is due to the fact that the HBI is melted in a blast furnace where the iron and slag are separated as usual. For this reason, the HBI required for electric steelmaking with the electric arc furnace (EAF) technology can be made of low-quality raw materials resulting in a high slag content and high impurities. In other words, as part of the iron oxide-containing feed fed to the blast furnace, HBI of insufficient quality for the EAF technology can be advantageously used, thereby further reducing the energy consumption and CO2 emissions of the shaft furnace plant.

[0058] Also, as described above, feeding cracked (or reformed) ammonia as a reducing gas to a blast furnace allows for a higher top gas temperature leaving the blast furnace, which allows for the use of larger amounts of HBI as input when compared to a blast furnace operated without the method, i.e., without the injection of cracked ammonia.

[0059] With high charging rates of HBI, significant reductions in CO2 emissions can be achieved. Reductions in CO2 emissions can also be achieved with the use of CO2-lean auxiliary fuels, e.g. COG. Nevertheless, the use of CO2-lean auxiliary fuels, e.g. COG, in combination with HBI will quickly reach the limits of conventional blast furnace operation and will not result in the total reduction in CO2 emissions that can be achieved individually with both HBI on the one hand and CO2-lean auxiliary fuels on the other hand. In fact, both the charging of HBI and the use of CO2-lean auxiliary fuels in the blast furnace reduce the top gas temperature of the blast furnace, so that the full combination of both process improvements (HBI charging and use of CO2-lean auxiliary fuels) is not allowed.

[0060] The shaft injection of reducing gas advantageously increases the top gas temperature, thereby balancing the cooling effect of HBI injection with the effect of using CO2-lean auxiliary fuel. Therefore, optimal CO2 savings are obtained when CO2-lean gas fuel injection through the tuyere of the blast furnace is combined with HBI injection in the blast furnace, shaft injection of hot reducing gas such as ammonia decomposition products (i.e., cracked or reformed ammonia). In a particularly preferred embodiment, the supply of cracked (i.e., reformed) ammonia as reducing gas in the blast furnace is combined with the supply of auxiliary fuel, such as coke oven gas (COG), and the supply of HBI as part of the iron oxide-containing input melted in the blast furnace. According to such an embodiment, the shaft injection of reformed ammonia, which generates a higher top gas temperature, results in lower CO2 emissions, in particular up to about 38%, as well as significant productivity increases, since the higher top gas temperature results in higher HBI and COG rates.

[0061] The expression "fluid connection" means that two devices are connected by a conduit or pipe so that a fluid, e.g., a gas, can flow from one device to another. This expression includes means for varying this flow, e.g., valves or fans for regulating the mass flow rate, compressors for regulating the pressure, etc., as well as control elements such as sensors, actuators, etc., that are necessary or desirable for proper control of the operation of the shaft furnace as a whole or of each element in a shaft furnace plant.

[0062] As used herein, "reformer" refers to a container, vessel, or the like in which a reforming process can take place, such as a reformer reactor or reforming vessel.

[0063] "Shaft feed," "shaft injection," "fed to shaft," "fed at shaft level," "fed through shaft," "fed at shaft level," or "injected at shaft level" refers to injecting material (such as gas) directly into the shaft of a shaft furnace. In embodiments where the shaft furnace is a blast furnace, this refers to injecting material above the hot blast furnace level, i.e., above the brim, and preferably into the ferrous oxide gas-solid reduction zone above the cohesive zone within the blast furnace.

[0064] In this specification, the terms "feeding to a shaft furnace" and "injecting into a shaft furnace", as well as "fed to a shaft furnace" and "injected into a shaft furnace" or "injected into a shaft furnace" are used synonymously, respectively, to mean the injection of material into a shaft furnace.

[0065] In this context, "about" means that a given numerical value covers a range of values ​​from -10% to +10% of that numerical value, preferably from -5% to +5% of that numerical value. Unless otherwise noted, all percentages herein relating to elemental and molecular proportions are expressed as wt% except for gas compositions, which are expressed as mol%.

[0066] Further details and advantages of the present disclosure will become apparent from the following detailed description of some non-limiting embodiments, with reference to the accompanying drawings. [Brief description of the drawings]

[0067] Preferred embodiments of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which: [Figure 1] FIG. 2 is a schematic diagram of a first variant embodiment of a shaft furnace plant configured for carrying out the method for operating a shaft furnace. [Diagram 2] FIG. 2 is a schematic diagram of a second variant embodiment of a shaft furnace plant configured for carrying out the method for operating a shaft furnace. Description of the Preferred Embodiments

[0068] In the following, two different variants of the shaft and the method of operating a shaft furnace plant are shown with reference to the attached drawings.

[0069] FIG. 1 shows an embodiment of a first embodiment of the present method for operating a shaft furnace, comprising reforming (i.e., decomposing) ammonia to produce a first reducing gas stream (i.e., decomposed ammonia) and injecting a first stream of the reducing gas through a shaft of the shaft furnace.

[0070] As shown diagrammatically in Figure 1, the shaft furnace plant 10 includes a shaft furnace 12 and a reforming plant 14 including an ammonia reformer in fluid communication with the shaft furnace 12. The shaft furnace 12 receives at its upper end a generally iron oxide-containing input 16. At the lower end of the shaft furnace 12, reduced iron and / or slag product 18 is removed.

[0071] Supplemental fuel 30 may be injected into the lower portion of the shaft furnace 12. The supplemental fuel may include coke oven gas, natural gas, or any other gas commonly used as a supplemental fuel for operating shaft furnaces.

[0072] The shaft kiln gas 32 leaving the shaft furnace 12 is recovered at its top end. The recovered shaft kiln gas 32 is usually pre-treated immediately upon leaving the shaft furnace 12. Pre-treatment of the shaft kiln gas 32 first involves cooling to reduce its steam content and then cleaning, in particular removing dust and / or HCl and / or metal compounds. In the embodiment of FIG. 1 , the cooling and cleaning of the shaft kiln gas 32 takes place in a cooling and cleaning unit 34.

[0073] Downstream of the cooling and scrubbing unit 34, the shaft furnace gas stream is split into at least two streams. One stream is called shaft furnace export gas 36 and can be fed to other units of the plant, including the current shaft furnace plant 10. The other stream 38 is used as part of the fuel gas in burners 40 of the ammonia reformer 14 to produce the energy needed to reform (i.e., decompose) the ammonia.

[0074] Alternatively or additionally, some of the shaft furnace gases may be diverted to another unit, such as a heat exchanger 42 , and then injected into the shaft furnace 12 and / or into the burners of the reformer 44 .

[0075] The other portion of the shaft furnace gas may be introduced directly into the ammonia reformer 14 via conduits 48 and 22 .

[0076] Shaft furnace gas (SFG) contains up to about 40% of the energy input to the shaft furnace. For the purpose of reducing the CO2 emissions from shaft furnace based metal (iron) production, one of the important strategies is to use this SFG for metallurgical purposes as much as possible. Therefore, in reforming or decomposition of ammonia to produce reducing gas, shaft furnace gas should be used as much as possible to improve the CO2 emission reduction potential from shaft furnace metal production.

[0077] The shaft furnace 12 receives reducing gas 20 at the shaft level. The reducing gas 20 reacts with the iron oxide-containing feed 16 inside the shaft furnace 12 to produce reduced iron oxide and metallic iron. DRI 18 is removed from the bottom of the furnace. According to the present embodiment, the reducing gas 20 is produced in the reforming plant 14, i.e. in an ammonia reformer. The reducing gas 20 is cracked ammonia 22 and contains N2 and H2. The reforming process takes place according to the following reaction: 2NH3 → N2 + 3H2

[0078] This may be maintained by high temperatures in the ammonia reformer and / or by the use of a catalyst, such as, for example, a Ni-based catalyst or any catalyst that operates at temperatures up to 1000° C. or at least up to 700° C. Ammonia 22 is supplied to the ammonia reformer 14 from a storage tank 24 that is in fluid communication with the reformer. In this particular configuration, the ammonia passes from the storage tank 24 through a heat exchanger 46 to heat the ammonia to ambient temperature.

[0079] 2, a second embodiment of the present shaft furnace plant 10 and method of operation is shown. In this embodiment, the shaft furnace is a blast furnace 112.

[0080] The blast furnace 112 typically receives coke (not shown) and ore from a storehouse. The ore is typically referred to as the iron oxide-containing input 16. According to the present embodiment, HBI 116 may also be fed into the top of the blast furnace 112 as part of the iron oxide-containing input 16 that is melted within the blast furnace 112.

[0081] At the lower end of the blast furnace 112, liquid pig iron and slag (i.e., iron product) 18 are extracted. The operation of the blast furnace 112 itself is well known and will not be described further here.

[0082] The blast furnace receives hot air 26 at the lower portion, or tuyere level, of the blast furnace 112 from a hot blast stove plant 28 consisting of multiple cowpers, and supplemental fuel 30. The hot air 26 may include air or oxygen-enriched gas. The supplemental fuel 30 may be pulverized coal, coke oven gas, natural gas, hydrogen, plastic waste, petroleum, lignite, ammonia, cracked ammonia, or any other gas commonly used as a supplemental fuel for operating a blast furnace.

[0083] The blast furnace 112 receives reducing gas 20 at the shaft level, located above the tuyere level. According to this embodiment, the reducing gas 20 is produced in a reforming plant 14, i.e. an ammonia reformer. The reducing gas is cracked ammonia 22, which comprises N2 and H2. The ammonia reformer comprises at least a burner 40, which is supplied with a fuel gas.

[0084] The reducing gas 20, with its high hydrogen content, is injected into the blast furnace 112 at shaft level.

[0085] The blast furnace gas 32 leaving the blast furnace 112 is recovered at its top. The recovered blast furnace gas 32 is usually pre-treated immediately upon leaving the blast furnace 112. Pre-treatment of the blast furnace gas 32 first involves cooling to reduce its steam content, then cleaning, in particular removing dust and / or HCl and / or metal compounds. In the embodiment of Fig. 2, the cooling and cleaning of the blast furnace gas is performed in a cooling and cleaning unit 34. Alternatively, separate units can be used, a first unit for cooling and a second unit (or multiple second units) for cleaning, or vice versa.

[0086] Downstream of the cooling and scrubbing unit 34, the blast furnace gas stream is split into at least two streams. One stream is called blast furnace export gas 36 and can be fed to other units of the steel plant, including the current shaft furnace plant 10. The other stream 38 is used as part of the fuel gas in the burners 40 of the ammonia reformer 14 to produce the energy needed to reform (i.e., crack) the ammonia.

[0087] Blast furnace gas (BFG) contains up to about 40% of the energy input to the blast furnace. For the purpose of reducing the CO2 emissions from blast furnace-based steelmaking, one of the important strategies is to use this BFG for metallurgical purposes as much as possible. Therefore, in the reforming or decomposition of ammonia to produce reducing gas, blast furnace gas should be used as much as possible to improve the CO2 emission reduction potential from blast furnace steelmaking.

[0088] The shaft furnace plant 10 described above with reference to Figure 2 may be operated to produce iron according to the method described herein. Table 1 compares classical operation of a blast furnace (base case) with operation of a blast furnace with cracked ammonia (i.e., first reducing gas stream) injection according to three embodiments of the method. [Table 1]

[0089] To calculate the CO2 emissions for different cases, the following emission factors were considered for different input materials (Table 2). [Table 2]

[0090] * Normally, HBI contains some carbon (approximately 1.5 wt.-%). In this case, green HBI, produced carbon-free, was used.

[0091] **CO2 emissions are already considered to be due to molten iron (molten iron).

[0092] In the reference operation, the blast furnace uses only coke and pulverized coal injection at the tuyere, whereas in case 1, cracked ammonia is additionally injected at shaft level (i.e., through the shaft) of the blast furnace. In case 1, 400 Nm 3 / tHM (Nm of molten iron 3 It can be seen that by injecting 1000 kg / tHM of decomposed ammonia through the shaft, the coke rate can be significantly reduced from 301 (for the reference) to 220 kg / tHM (for case 1). The CO2 emissions are reduced from 1973 (for the reference) to 1634 kg / tHM (for case 1), making it possible to reduce the CO2 emissions by 17%. The rate expressed in " / tHM" refers to per ton (metric ton) of hot metal produced in the shaft furnace. "Nm 3 " refers to normal lube, which indicates the volume of 1 cubic meter of gas under normal conditions, i.e., a temperature of 0°C (273.15 K) and an absolute pressure of 1 atmosphere (101.325 kPa).

[0093] In Case 2 (Table 1), cracked ammonia (as in Case 1) is injected at the shaft level of the blast furnace, and coke oven gas (COG) is injected through the tuyere of the blast furnace. Increasing the amount of auxiliary fuel (e.g. COG) injected requires increasing oxygen enrichment to maintain flame temperatures, which are typically above 2000°C with PCI and above 1800°C without PCI.

[0094] Increasing oxygen enrichment in the blast furnace means reducing the amount of natural blast (air) used in the blast furnace. As a result, the total amount of hot air entering the blast furnace was reduced from 830 (for the standard) to 412 Nm 3 / tHM (for case 2).

[0095] As is evident from Case 2 in Table 1, simultaneous COG injection and pulverized coal injection are possible, allowing a sufficient top gas temperature of about 169°C. COG injection allows a further reduction in the coke rate from 220 kg / tHM (for Case 1) to 202 kg / tHM (for Case 2). This reduces the associated CO2 emissions from 1634 kg / tHM (for Case 1) to 1528 kg / tHM (for Case 2), corresponding to an additional CO2 emission reduction of 6%. Compared to the reference case, CO2 emissions are reduced by only 23% in Case 2.

[0096] In the final case (Case 3) shown in Table 1, HBI is provided as part of the iron oxide-containing input in addition to the injection of cracked ammonia and COG. The supply of HBI allows a reduction in the coal rate (i.e. pulverized coal injection rate) while maintaining essentially the same coke rate compared to Case 2 (202 vs. 201 kg / tHM), which is expected and corresponds to the minimum coke rate at which the blast furnace can be operated to ensure the required permeability in the gas-solid-liquid reactor. It can be seen that the reduction in the overall carbon input leads to a further reduction in CO2 emissions, which are only 1221 kg / tHM, corresponding to a 38% reduction in CO2 emissions compared to the reference case.

[0097] From Table 1, it can be seen that replacing a portion of the coke with cracked ammonia increases the low heating value top gas and increases the downstream utilization efficiency of the top gas (i.e., blast furnace gas) in the power plant and / or other furnaces. Further reduction in the coke rate by injection of coke oven gas (COG) as a supplemental fuel and / or HBI as an iron oxide-containing input can further increase the low heating value top gas.

[0098] While the invention has been illustrated and described in detail in the drawings and the foregoing description, such illustration and description are illustrative or exemplary and not restrictive. The invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. [Explanation of symbols]

[0099] 10. Shaft Furnace Plant 12 Shaft furnace 14 Ammonia reforming plant / reformer 16 Iron oxide-containing inputs 18 Iron Products 20 Reducing Gas 22 Ammonia NH3 24 Ammonia NH3 storage tank 26 Hot air 28 Hot Stove Plant 30 Auxiliary fuel 32 Blast furnace gas 34 Cooling and cleaning unit 36 Export Gas 38 Pretreated blast furnace gas 40 Burner 42 Heat exchanger 44 Reformer 46 Heat exchanger 48 Conduit 112 Blast Furnace 116 Hot Briquette Iron (HBI)

Claims

1. A method of operating a blast furnace plant (10) including a blast furnace (12, 112) and an ammonia reforming plant (14), comprising the steps of: a. feeding an ammonia stream (22) to an ammonia reforming plant (14); b. cracking said ammonia stream (22) in an ammonia reforming plant (14) to produce a reducing gas (20); c. Feed the iron oxide containing charge (16) and reducing gas (20) into a blast furnace (12, 112); d. reducing the iron oxide in the blast furnace (12, 112) by reaction with the iron oxide-containing charge (16) and the reducing gas (20); The method wherein the reducing gas (20) comprises less than 15% ammonia.

2. 10. The method of claim 1, wherein the decomposition in step b) is carried out catalytically.

3. 3. The method of claim 1 or 2, further comprising recovering a top gas stream (32) from the blast furnace (12, 112) and combusting said top gas stream in a burner (40) of an ammonia reforming plant (14).

4. 3. The method of claim 1 or 2, further comprising the step of supplying one or more of other reducing agents, carburizing agents and fuels, and reducing gases or mixtures thereof to the blast furnace.

5. 3. A method according to claim 1 or 2, wherein a biofuel such as steel plant gas, ammonia itself or biogas, biomass or a mixture thereof is used in the burner (40) of the ammonia reforming plant (14).

6. 3. The method of claim 1 or 2, wherein the energy used to heat or vaporize the ammonia to room temperature is used to meet cooling needs in the steel plant, such as air conditioning or cooling water.

7. 3. The method according to claim 1 or 2, wherein the blast furnace comprises a shaft and the supply of the reducing gas (20) is made directly via the shaft of the blast furnace (12, 112).

8. 3. The method of claim 1 or 2, wherein one or more of the auxiliary fuel, the reducing agent, and the carburizing agent (30) are supplied to the blast furnace (12, 112) in addition to the reducing gas (20).

9. 9. The method of claim 8, wherein the supplemental fuel (30) is pulverized coal, natural gas, coke oven gas, biogas, syngas, ammonia, cracked ammonia, hydrogen, or mixtures thereof, fed to the blast furnace at the tuyere level.

10. 3. The method of claim 1 or 2, wherein a synthesis gas stream is fed to the blast furnace (12, 112) in addition to the reducing gas (20), and an iron product is also produced by reaction of the synthesis gas stream and an iron oxide-containing input (16).

11. 11. The method of claim 10, wherein the synthesis gas stream is produced by reforming an industrial gas and a fuel gas.

12. 12. The method of claim 11, wherein hot briquetted iron (HBI) (116) or scrap is fed to the blast furnace (112) as part of the iron oxide-containing input (16).

13. A blast furnace plant (10) configured to carry out the method according to claim 1 or 2, comprising: Blast furnaces (12, 112); and 1. A blast furnace plant comprising: an ammonia reforming plant (14) having a gas inlet and a gas outlet, the gas inlet being fluidly connected to an ammonia source (24) or a heat exchanger, and the gas outlet being fluidly connected to a blast furnace (12, 112).

14. 14. A blast furnace plant (10) according to claim 13, wherein the top of the blast furnace is in fluid connection with a burner (40) of the ammonia reforming plant (14).

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