Method for operating plant comprising direct reduction reactor

Abstract

To provide a method for operating a shaft furnace plant as well as a corresponding shaft furnace plant which reduce the CO2 emissions resulting from operation of a shaft furnace.SOLUTION: A method for operating a shaft furnace plant comprising a shaft furnace and an ammonia reforming plant is provided, the method comprising the steps of (a.) feeding a stream of ammonia to the ammonia reforming plant; (b.) cracking the stream of ammonia in the ammonia reforming plant to produce a stream of reducing gas; (c.) feeding a metal oxide-containing charge, e.g. an iron oxide-containing charge and the stream of reducing gas into the shaft furnace; and (d.) reducing the metal oxide inside the shaft furnace by reaction between the metal oxide-containing charge and the stream of reducing gas. The reducing gas comprises less than 15% of ammonia, preferably less than 10% of ammonia. The present invention also relates to a shaft furnace plant configured to implement such a method.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates generally to a method for operating a shaft furnace plant and to such a shaft furnace installation. In particular, the present invention relates to a method for operating 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 means it is essential that sectors step up to 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 steel production today, and efforts have been made for many years to reduce CO2 emissions from blast furnaces 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 perspective, and often from an economic perspective, it is a less desirable energy source.

[0005] Primarily to reduce coke consumption, 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 in the reduction process. One way to do this is to reduce the CO2 content in blast furnace gas by pressure swing adsorption (PSA) or vacuum pressure swing adsorption (VPSA). PSA / VPSA systems produce 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 returned to the blast furnace. PSA / VPSA systems can reduce the CO2 content in blast furnace gas from approximately 40 mol-% to approximately 5 mol-%, but they are very expensive to acquire, maintain, and operate, and require a lot of space.

[0006] Considerable effort has also been 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, pulverized coal is mainly 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 have already been reached. Indeed, the higher the hydrogen contribution, the greater the CO2 reduction potential of blast furnace operation. However, injecting cold H2 and / or hydrocarbons through the tuyere, along with large amounts of pulverized coal (PCI), significantly reduces RAFT (raceway adiabatic flame temperature). To increase RAFT, 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 savings potential of this technology.

[0008] Furthermore, some countries do not have sufficient green energy available to meet the needs of steel plants. Also, producing and / or importing hydrogen is very costly, difficult, and requires specific infrastructure. Therefore, there remains a need for alternative methods of supplying 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 and a corresponding shaft furnace plant which reduces 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 a shaft furnace plant according to claim 15. [Means for solving the problem]

[0011] In order to achieve the above object, in a first aspect, the present invention proposes a method for operating a shaft furnace plant including a shaft furnace and an ammonia reforming plant, the method comprising: a. Supplying 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 into 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. Although the method can be applied to produce other metals such as lead or copper from corresponding metal oxide-containing charges, 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.

[0013] The method is particularly adapted to a preferred embodiment in which the shaft furnace is a direct reduction reactor, 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 a metal / iron oxide-containing input during oxidation, thereby producing metal / iron. Herein, 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 containing iron oxide 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 ore 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(HO), 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 the present disclosure, a reforming plant is an ammonia reforming plant (also referred to as 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, for direct reduction reactors, 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, H and smaller amounts of CH, N, H0, CO, etc.).

[0019] In embodiments, 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 in parallel with each other to form at least two reformers in series. In embodiments where the ammonia reforming plant includes multiple reformers, the reformers may be identical to or different from each other. The exact number, type and arrangement of reformers in the ammonia reforming plant may be advantageously adapted to meet the requirements of the reducing gas produced (e.g., temperature, ammonia residual amount, etc.) and the subsequent feeding of the reducing gas produced to the shaft furnace.

[0020] In another aspect, the present invention also provides a method for producing a pharmaceutical composition 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.

[0021] The shaft furnace plant is advantageously configured to be able to operate by carrying out the method according to the first aspect, as will be explained in more detail below.

[0022] Thus, the present disclosure proposes an integrated method and corresponding plant that allows the operation of shaft furnaces with reduced coke and / or other carbon sources, with low CO2 emissions and optimal use of existing infrastructure.

[0023] The present 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 while maintaining much of the existing infrastructure.

[0024] In fact, the inventors have found that this operating method is very compatible with each country's CO2 lean energy strategy. The transportation of ammonia can be realized using facilities 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 atmospheric pressure, it can be relatively easily adapted to existing infrastructure. Thus, it is compatible with common LPG and / or LNG facilities.

[0025] To reduce CO2 emissions in steel plants, ammonia can be used directly as additional fuel gas in burners, such as those in hot stove plants, reheating furnaces, and thermal power plant burners. When ammonia is used directly in burners, problems with NOx emissions associated with the combustion of nitrogen-rich ammonia fuel are encountered. These problems are avoided when high-temperature decomposed 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 contributes to the outgoing top gas with the components H2, H2O, and N2. When H2O is condensed, the outgoing top gas is enriched only in N2 and H2, minimizing its impact on NOx formation during combustion. Another positive effect is that the outgoing top gas has an increased lower calorific value, leading to higher efficiencies and therefore reduced energy consumption in downstream furnaces and thermal power plants that use the top gas from the shaft furnace.

[0026] Therefore, the main advantage of the proposed method is that it identifies how to improve the efficiency of ammonia use in steel plants, especially shaft furnaces, in order to further reduce CO2 emissions.

[0027] Another advantage is that the reforming (i.e., cracking) process allows for the highly efficient production of synthesis gas with a high hydrogen (H2) content from ammonia.

[0028] Furthermore, the decomposition of ammonia is a highly endothermic reaction and requires a great deal of energy to carry 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, thus strongly reducing the temperature at the injection point and thereby slowing the reaction between the reducing gas and the iron oxide-containing charge. To compensate for the cooling effect of the undecomposed ammonia injection, more coke must be injected, thereby negatively impacting the potential for CO2 emission reduction. Therefore, decomposing ammonia outside the shaft furnace prevents the consumption of excess carbon-containing reducing agent during shaft furnace operation and can significantly reduce the CO2 emissions of a shaft furnace plant.

[0029] 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 being fed 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.

[0030] 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.

[0031] 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 shutting down the shaft furnace.

[0032] 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.

[0033] These and further advantages of the present method for operating a shaft furnace and the shaft furnace plant of the present disclosure are described in further detail below.

[0034] As mentioned above, the decomposition of ammonia occurs according to the following reaction: 2NH3 → N2 + 3H2 The decomposition (i.e., reforming) of ammonia requires a high activation energy, making the use of a catalyst useful. At high temperatures, i.e., the 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 longer residence time of the ammonia in at least one reformer of the ammonia reforming plant, which may require a larger reformer.

[0035] Thus, the reforming (ie, decomposition) of ammonia can be carried out catalytically or non-catalytically.

[0036] Additionally, catalysts can be used to provide the endothermal heat required for the decomposition (i.e., reforming or cracking) of ammonia at low temperatures. This is even more important because decomposition (i.e., reforming) requires very high energy, similar to the energy required to heat ammonia from ambient temperature to about 1000°C. Therefore, performing 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.

[0037] Currently, catalyst development for ammonia decomposition (i.e., ammonia reforming) is still ongoing. Any type of catalyst can be used in this process, such as nickel-based catalysts or any catalyst that operates at high temperatures, i.e., up to about 1000°C. However, catalysts that operate near about 500°C, the expected thermodynamic temperature at which high ammonia conversion rates are obtained, can be used advantageously in the reformer to increase thermal efficiency.

[0038] It is advantageous to have as high ammonia conversion 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 because the decomposition of ammonia is endothermic, which cools the atmosphere in the shaft furnace and therefore has a negative impact on the shaft furnace process. In fact, a reducing gas containing 10 mol% ammonia will reduce its temperature by approximately 40°C when this ammonia is converted adiabatically.

[0039] Surprisingly, the inventors have found that when operating a shaft furnace plant in this manner, residual ammonia levels in the reducing gas are not an issue, nor is it necessary to carry out ammonia reforming (i.e., decomposition) at low temperatures, since the resulting reducing gas needs to be at high temperatures, typically above 800°C, in order to inject it into the shaft furnace.

[0040] As mentioned above, the reducing gas may contain ammonia, i.e., undecomposed (or unreformed) ammonia. Depending on the requirements of the shaft furnace, 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. Because the ammonia reforming process does not need to be perfect, it is an easy quick win for efficient use of ammonia to reduce CO2 emissions in the shaft furnace.

[0041] 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.

[0042] The pressure of the reforming process, i.e. the pressure at which the cracking is carried out, preferably corresponds to the pressure at shaft level of the blast furnace, plus the pressure losses in the ducts and reformer. Typical pressure levels at the inlet of a reforming plant will be below about 15 barg, more particularly below 12 barg.

[0043] Advantageously, the ammonia reforming plant may include a heat exchanger, such as room air conditioning, cooling water cooling, etc., arranged to supply cooling energy resulting from the heating, and possibly evaporation, of the ammonia stream provided from the ammonia store to the at least one reformer to consumers within the steel plant.

[0044] 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.

[0045] The heat exchanger can be of various types, such as tube bundle type, plate type heat exchanger, etc.

[0046] 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 the gas exiting the top of the shaft 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, etc. or mixtures thereof may be used in the burner of the ammonia reforming plant.

[0047] As mentioned above, a lot of energy is used in heating and decomposing (i.e., reforming) ammonia. Heating ammonia from gas to about 25°C to 950°C and reforming (i.e., decomposing) it into hydrogen H2 and nitrogen N2 requires about 4.5 MJ / Nm 3 of ammonia NH3 is required. This energy can advantageously be provided by burning top gases from the shaft furnace in the burners of the ammonia reforming plant, making it possible, for metallurgical reasons, to recycle the energy of the shaft furnace gases directly to the shaft furnace instead of using it for energy-inefficient electrical energy production. Since no additional 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, etc. or mixtures thereof are used in the burners of the ammonia reforming plant.

[0048] According to a preferred embodiment, the reducing gas is supplied directly through the shaft of the shaft furnace. In embodiments where the shaft furnace is a direct reduction reactor, this means that the reducing gas is preferably injected into the reduction zone, rather than into the throat or cooling zone of the reactor. In embodiments where the shaft furnace is a blast furnace, this means that the reducing gas can be injected at shaft level, i.e., above the hot blast level, preferably above the cohesive zone, into the ferrous oxide gas solid reduction zone. Injecting the produced reducing gas at the shaft level of the blast furnace can significantly reduce the coke rate, i.e., the coke and / or other carbon sources per ton of pig iron produced.

[0049] Alternatively or additionally, reducing gas can be injected at the tuyere level of the blast furnace, preferably at a high temperature after decomposition. While injecting reducing gas through the tuyere increases the oxygen required for blast furnace operation, thereby generally reducing the need for supplemental fuel addition, reducing gas containing decomposed ammonia can be advantageously injected at the tuyere level at a high temperature after decomposition, regardless of whether O2 is added to heat the furnace to flame temperature in the raceway or whether plasma heating outside the furnace already reaches flame temperature. Therefore, reducing gas containing decomposed ammonia can be injected at the tuyere level regardless of whether (reducing) gas is injected at the lower shaft. Furthermore, reducing gas containing decomposed ammonia can be injected at the tuyere level regardless of whether recycled and cooled (condensed) shaft furnace top gas, previously heated directly and / or indirectly to 700-1000°C, is injected at the upper shaft level.

[0050] In a preferred embodiment, in addition to the reducing gas injected into the shaft of the blast furnace, an auxiliary fuel is supplied into the blast furnace. The auxiliary fuel can advantageously be pulverized coal, natural gas, coke oven gas, and / or hydrogen. Injecting reducing gas into a shaft furnace, particularly the shaft of a blast furnace, allows for the injection of pulverized coal, natural gas, particularly hydrogen, or other materials at higher tuyeres. In fact, injecting (or supplying) cracked ammonia into the shaft as reducing gas increases the top gas temperature, thereby allowing for higher oxygen enrichment at the tuyeres, thus enabling the injection of higher auxiliary fuels such as PCI, NG, COG, hydrogen, etc. As mentioned above, cracked ammonia and / or ammonia containing reducing gas can also be added (as auxiliary fuel) at the tuyeres, with or without O2 addition, with or without additional plasma heating, and with or without reducing gas injection at the lower shaft. In this way, the excess 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, consequently, CO2 emissions.

[0051] In some embodiments, a synthesis gas stream is fed to the shaft furnace in addition to the reducing gas, and in such embodiments, iron reduction is also produced by reaction between the synthesis gas stream and the iron oxide-containing input.

[0052] 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.).

[0053] 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.

[0054] HBI is an interesting form of energy transport because it combines ease of transportation with high energy density. In fact, its compact shape makes it easy to handle and transport, allowing HBI to be transported using existing infrastructure. HBI is compressed direct reduced iron, i.e., pre-processed iron ore, and its transportation advantageously combines the transport of raw materials supplied as iron oxide-containing inputs in blast furnaces with the transport of energy, while avoiding the transport of oxygen bound to unreduced ore. In fact, because HBI is pre-processed iron ore, less energy is required to obtain fully processed iron in a blast furnace, since HBI already has a high metallic iron content.

[0055] To achieve significant CO2 savings, HBI is preferably produced with green hydrogen, or alternatively, it can be produced from natural gas, with carbon capture applied to the hydrogen and / or DRI production process.

[0056] The HBI fed to the blast furnace has the additional advantage that 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 normally separated. For this reason, the HBI required for electric steelmaking using the electric arc furnace (EAF) technology can be made from low-quality raw materials, resulting in a high slag content and high impurities. In other words, HBI of insufficient quality for EAF technology can be advantageously used as part of the iron oxide-containing feed fed to the blast furnace, thereby further reducing the energy consumption and CO2 emissions of the shaft furnace plant.

[0057] Furthermore, as described above, feeding cracked (or reformed) ammonia as a reducing gas to a blast furnace can increase the temperature of the top gas exiting the blast furnace, which allows for the use of larger amounts of HBI as input compared to a blast furnace operated without the method, i.e., without the injection of cracked ammonia.

[0058] High charging rates of HBI can achieve significant reductions in CO2 emissions. Reductions in CO2 emissions can also be achieved by using lean CO2 supplemental fuels, for example, COG. Nevertheless, the use of lean CO2 supplemental fuels, such as COG, in combination with HBI quickly reaches the limits of conventional blast furnace operation and will not result in the total CO2 reductions that can be achieved by using both HBI on the one hand and lean CO2 supplemental fuel on the other hand separately. In fact, both the injection of HBI into the blast furnace and the use of lean CO2 supplemental fuel reduce the blast furnace top gas temperature, and therefore do not allow the full combination of both process improvements (HBI injection and the use of lean CO2 supplemental fuel) to be achieved.

[0059] Shaft injection of reducing gas advantageously increases the top gas temperature, thereby balancing the cooling effect of HBI injection with the effect of using lean CO2 auxiliary fuel. Therefore, optimal CO2 savings are achieved when lean CO2 fuel injection through the tuyere of the blast furnace is combined with shaft injection of hot reducing gas, such as HBI injection into the blast furnace and ammonia decomposition products (i.e., cracked or reformed ammonia). In a particularly preferred embodiment, the supply of cracked (i.e., reformed) ammonia as the reducing gas in the blast furnace is combined with the supply of auxiliary fuel, such as coke oven gas (COG), and HBI as part of the iron oxide-containing input material melted in the blast furnace. According to such an embodiment, shaft injection of reformed ammonia, which generates higher top gas temperatures, results in higher HBI and COG rates, resulting in lower CO2 emissions, particularly up to about 38%, and significant productivity improvements.

[0060] The term "fluid connection" means that two devices are connected by a conduit or pipe, allowing a fluid, e.g., a gas, to flow from one device to another. This term includes means for varying this flow, such as valves or fans for adjusting mass flow, compressors for adjusting pressure, etc., as well as sensors, actuators, and other control elements necessary or desirable for proper control of the operation of the shaft furnace as a whole or of each element within the shaft furnace plant.

[0061] As used herein, the term "reformer" refers to a container, vessel, or the like, in which a reforming process can occur, such as a reformer reactor or reforming vessel.

[0062] "Shaft-fed," "shaft-injected," "fed to a shaft," "fed at shaft level," "fed through a shaft," "fed at shaft level," or "injected at shaft level" refers to the injection of 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 the injection of material above the hot blast furnace level, i.e., above the bosh, preferably within the ferrous oxide gas-solid reduction zone above the cohesive zone within the blast furnace.

[0063] In this document, 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.

[0064] 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 specified, all percentages herein relating to elemental and molecular proportions are expressed as wt% except for gas compositions, which are expressed as mol%.

[0065] 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 explanation of the drawings]

[0066] 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] 1 is a schematic diagram of a first variant embodiment of a shaft furnace plant configured to implement the method for operating a shaft furnace. [Figure 2] 1 is a schematic diagram of a second variant embodiment of a shaft furnace plant configured to implement the method for operating a shaft furnace. DESCRIPTION OF THE PREFERRED EMBODIMENT

[0067] In the following, two different variants of the shaft and the method of operating the shaft furnace plant are shown in relation to the attached drawings.

[0068] FIG. 1 shows an embodiment of a first embodiment of the present method for operating a shaft furnace, which includes reforming (i.e., decomposing) ammonia to produce a first reducing gas stream (i.e., decomposed ammonia) and injecting the first stream of reducing gas through the shaft of the shaft furnace.

[0069] As shown schematically 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 slag product 18 are removed.

[0070] Supplemental fuel 30 may be injected into the lower part 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 a shaft furnace.

[0071] The shaft furnace gas 32 leaving the shaft furnace 12 is recovered at its top end. The recovered shaft furnace gas 32 is usually pre-treated immediately upon leaving the shaft furnace 12. Pre-treatment of the shaft furnace gas 32 involves first cooling to reduce its vapor content, then cleaning, in particular removing dust and / or HCl and / or metal compounds. In the embodiment of Figure 1, the cooling and cleaning of the shaft furnace gas 32 takes place in a cooling and cleaning unit 34.

[0072] 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 in the plant, including the current shaft furnace plant 10. The other stream 38 is used as part of the fuel gas in the burner 40 of the ammonia reformer 14 to produce the energy needed to reform (i.e., decompose) the ammonia.

[0073] 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 .

[0074] Another portion of the shaft furnace gas may be introduced directly into the ammonia reformer 14 via conduits 48 and 22 .

[0075] Shaft furnace gas (SFG) contains up to approximately 40% of the energy input to a shaft furnace. To reduce CO2 emissions from shaft furnace-based metal (iron) production, one of the key strategies is to use this SFG for metallurgical purposes as much as possible. Therefore, reforming or decomposition of ammonia to produce reducing gas should use shaft furnace gas as much as possible to improve the CO2 emission reduction potential from shaft furnace metal production.

[0076] 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 lower side of the furnace. According to this 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 occurs according to the following reaction: 2NH3 → N2 + 3H2

[0077] This may be maintained by high temperatures within the ammonia reformer and / or by the use of a catalyst, such as a Ni-based catalyst or any catalyst that operates at temperatures up to 1000° C. or at least 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.

[0078] 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.

[0079] The blast furnace 112 typically receives coke (not shown) and ore from a storehouse, which is typically referred to as iron oxide-containing charge 16. According to this embodiment, HBI 116 may also be fed into the top of the blast furnace 112 as part of the iron oxide-containing charge 16 that is melted within the blast furnace 112.

[0080] At the lower end of the blast furnace 112, liquid pig iron and slag (i.e., iron products) 18 are extracted. The operation of the blast furnace 112 itself is well known and will not be described further here.

[0081] The blast furnace receives hot blast 26 at the lower portion of the blast furnace 112, i.e., at the tuyere level, provided by a hot blast stove plant 28 consisting of multiple cowpers, and supplemental fuel 30. The hot blast 26 may include air or oxygen-enriched gas. The supplemental fuel 30 may be pulverized coal, coke oven gas, natural gas, hydrogen, plastic waste, oil, lignite, ammonia, cracked ammonia, or any other gas commonly used as a supplemental fuel for operating a blast furnace.

[0082] The blast furnace 112 receives reducing gas 20 at a shaft level 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 contains N2 and H2. The ammonia reformer includes at least a burner 40 supplied with fuel gas.

[0083] The reducing gas 20, with its high hydrogen content, is injected into the blast furnace 112 at shaft level.

[0084] The blast furnace gas 32 leaving the blast furnace 112 is recovered at its top end. 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 involves first cooling to reduce its steam content, then cleaning, in particular removing dust and / or HCl and / or metal compounds. In the embodiment of Figure 2, the cooling and cleaning of the blast furnace gas takes place 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.

[0085] 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 burner 40 of the ammonia reformer 14 to produce the energy needed to reform (i.e., decompose) the ammonia.

[0086] Blast furnace gas (BFG) contains up to approximately 40% of the energy input to a blast furnace. With the aim of reducing CO2 emissions from blast furnace-based steelmaking, one of the key strategies is to use this BFG for metallurgical purposes as much as possible. Therefore, reforming or decomposition of ammonia to produce reducing gas should use blast furnace gas as much as possible to improve the potential for reducing CO2 emissions from blast furnace steelmaking.

[0087] The shaft furnace plant 10 described above with reference to Figure 2 can be operated to produce iron in accordance with 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 in accordance with three embodiments of the method. [Table 1]

[0088] To calculate the CO2 emissions for different cases, the following emission factors were considered for different input materials (Table 2). [Table 2]

[0089] * Typically, HBI contains some carbon (approximately 1.5 wt.-%). In this case, green HBI, which is produced carbon-free, was used.

[0090] **CO2 emissions are already considered to be due to molten iron (hot metal).

[0091] 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 hot metal 3 It can be seen that by injecting cracked ammonia at a rate of Nm / t through the shaft, the coke rate can be significantly reduced from 301 (for the reference) to 220 kg / tHM (for Case 1). CO2 emissions are reduced from 1973 (for the reference) to 1634 kg / tHM (for Case 1), enabling a 17% reduction in CO2 emissions. The rate expressed in " / tHM" refers to per ton (metric ton) of hot metal produced in the shaft furnace. "Nm 3 " refers to the normal lube, which indicates the volume of one cubic meter of gas under normal conditions, i.e., a temperature of 0°C (273.15K) and an absolute pressure of 1 atmosphere (101.325kPa).

[0092] 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 blast furnace tuyeres. 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.

[0093] 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 has decreased from 830 (relative to the standard) to 412 Nm3. 3 / tHM (for case 2).

[0094] As is evident from Case 2 in Table 1, simultaneous COG injection and pulverized coal injection are possible, allowing for a sufficient top gas temperature of approximately 169°C. COG injection allows for 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 base case, CO2 emissions are reduced by only 23% in Case 2.

[0095] In the final case (Case 3) shown in Table 1, HBI is supplied as part of the iron oxide-containing input in addition to the injection of cracked ammonia and COG. The supply of HBI allows for a reduction in the coal rate (i.e., pulverized coal injection rate) while maintaining essentially the same coke rate relative to Case 2 (202 vs. 201 kg / tHM). This coke rate is expected to correspond to and represents the minimum coke rate at which the blast furnace can be operated to ensure the necessary permeability to the gas-solid-liquid reactor. The reduction in overall carbon input further reduces CO2 emissions, which are only 1221 kg / tHM, representing a 38% reduction in CO2 emissions relative to the base case.

[0096] Table 1 shows that replacing a portion of the coke with cracked ammonia increases the low heating value of the top gas and improves downstream utilization of the top gas (i.e., blast furnace gas) in power plants and / or other furnaces. Further reduction in the coke rate through 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 of the top gas.

[0097] While the invention has been illustrated and described in detail in the drawings and 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]

[0098] 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 shaft furnace plant (10) including a shaft furnace (12) and an ammonia reforming plant (14), wherein the shaft furnace (12) is a direct reduction reactor; 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 iron oxide containing charge (16) and reducing gas (20) into the shaft furnace (12); d. reducing the iron oxide in the shaft furnace (12) by reaction with the iron oxide-containing charge (16) and a 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 shaft furnace (12) 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 shaft 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, wherein the shaft furnace comprises a shaft and the supply of the reducing gas (20) is carried out directly via the shaft of the shaft furnace (12).

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

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

10. 10. The method of claim 9, wherein the synthesis gas stream is produced by reforming an industrial gas and a fuel gas.

11. A shaft furnace plant (10) configured to carry out the method according to claim 1 or 2, comprising: A shaft furnace (12) that is a direct reduction reactor; and 1. A shaft furnace plant comprising: an ammonia reforming plant (14) with 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 shaft furnace (12).

12. 12. The shaft furnace plant (10) according to claim 11, wherein the top of the shaft furnace (12) is in fluid connection with a burner (40) of the ammonia reforming plant (14).

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