Method for operating a blast furnace plant and blast furnace plant

Abstract

This invention provides a method for operating a shaft furnace comprising a shaft furnace and an ammonia reforming unit, the method comprising the steps of: (a) supplying an ammonia stream to the ammonia reforming unit; (b) cracking the ammonia stream in the ammonia reforming unit to produce a reducing gas stream; (c) supplying a charge containing metal oxides, such as an iron oxide charge, and a reducing gas stream to the shaft furnace; and (d) reducing the metal oxides inside the shaft furnace by a reaction between the metal oxide-containing charge and the reducing gas stream, wherein the reducing gas contains less than 15% ammonia, preferably less than 10%. This invention also relates to a shaft furnace configured to carry out this method.

Description

Technical field

[0001] The invention relates generally to a method for operating a shaft furnace plant and to such a shaft furnace arrangement. In particular, the invention relates to a method for operating a blast furnace plant or a plant containing a direct reduction reactor. prior art

[0002] With the Paris Agreement and near-global consensus on the need for emissions action, every industrial sector is eager to develop solutions to improve energy efficiency and reduce CO2 output.

[0003] In this context, players in the ferrous metallurgical sector have developed novel methods to reduce the environmental footprint of blast furnace smelting railway lines. In fact, despite alternatives such as scrap melting or direct reduction in electric arc furnaces, blast furnaces (BF) are currently the most widely used method for steel production, and efforts have been made over the years to reduce CO2 emissions from blast furnaces. In order to contribute to the global reduction of CO2 emissions.

[0004] Coking coal is the main energy input for blast furnace ironmaking. From a CO 2 and often from an economic point of view, this is a less favorable energy source.

[0005] Primarily to reduce the amount of coking coal used, a strategy was developed to recover the blast furnace top gas from the blast furnace, treat it to increase its reduction potential, and reinject it back into the blast furnace to assist in the reduction process. One way to achieve this is to reduce the CO2 content in the blast furnace gas through pressure swing adsorption (PSA) or vacuum pressure swing adsorption (VPSA). The PSA / VPSA unit produces a first gas stream rich in CO and H2 and a second gas stream rich in CO2 and H2O. The first gas stream can be used as reducing gas and fed back to the blast furnace. Although PSA / VPSA devices can reduce the CO 2 content in blast furnace gases from about 40 mol-% to about 5 mol-%, these devices are very expensive to purchase, maintain and operate, and require a lot of space.

[0006] Along with reducing CO2 emissions, considerable efforts are also being made to reduce the use of carbon-containing fuels for the operation of the blast furnace itself. Nowadays, it is widely used to replace coking coal with other energy sources, mainly injected at the tuyere height. Due to cost reasons, pulverized coal is mainly injected. Alternatively, fuels with increased hydrogen content in the form of hydrocarbons, gaseous hydrogen H2 or mixtures thereof are mainly used in countries where natural gas prices are low. Hydrogen and hydrocarbons with rich calorific value have the potential to be injected into the blast furnace tuyere as auxiliary fuel.

[0007] These auxiliary fuels have a positive impact on CO2 emissions from blast furnace steelmaking, but their use is limited due to methodological reasons, and these limits are now frequently reached. In fact, the more hydrogen is involved, the higher the CO reduction potential of the blast furnace operation in general. However, the injection of cold H2 and / or hydrocarbons and a large amount of pulverized coal (PCI) through the tuyeres will cause a significant decrease in RAFT (trough plate adiabatic flame temperature). To increase RAFT, higher oxygen enrichment is required, but is limited by top gas temperature. Therefore, only a relatively small amount of cold H2 and / or hydrocarbons can be injected into the blast furnace through the tuyere, which limits the CO2 emission reduction potential of this technology.

[0008] In addition, in some countries, there is not enough green energy available to meet the needs of steelmaking equipment. In addition, the production and / or import of hydrogen is very expensive and difficult, requiring specific infrastructure. Therefore, there is still a need for alternative methods of supplying hydrogen-rich gas to shaft furnaces, specifically to blast furnaces. Contents of the invention

[0009] [technical problem] []

[0010] 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 reduce the CO 2 emissions produced by operating the shaft furnace and at least partially overcome the above-mentioned problems.

[0011] This object is achieved by the method as in Item 1 of the patent application and the shaft furnace equipment as in Item 15 of the Patent Application. [General description of the invention] []

[0012] In order to achieve this goal, the present invention proposes a method for operating a shaft furnace equipment including a shaft furnace and an ammonia reforming equipment in a first aspect. The method includes the following steps: a. Supply the ammonia flow to the ammonia reforming equipment; b. Crack the ammonia stream in an ammonia reformer to produce reducing gas; c. Feed the metal oxide-containing charge to the shaft furnace; d. Reduce the metal oxide in the shaft furnace through the reaction between the metal oxide charge and the reducing gas.

[0013] 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 the production of other metals (such as lead or copper) from corresponding metal oxide-containing charges, the shaft furnace is preferably used for the production of iron (from iron oxide-containing charges), such as pig iron, slag, direct reduction Iron (sponge iron), hot pressed iron (HBI), etc.

[0014] This method is particularly applicable to preferred embodiments in which the shaft furnace is a direct reduction reactor or a blast furnace. However, this method can be implemented to operate a shaft furnace plant containing any type of shaft furnace.

[0015] In the context disclosed herein, reducing gas involves a gas capable of reducing metal oxide / iron oxide-containing charge while oxidizing it, thereby producing metal / iron gas. Herein, ammonia cracking may also be referred to as ammonia recombination, such that the reducing gas may also be referred to as cracked ammonia, and unreacted ammonia may be referred to as unreacted ammonia or unrecombined ammonia.

[0016] In the context disclosed herein, an iron oxide-containing charge refers to materials containing iron hydroxides, iron oxide-hydroxides, iron oxides, such as iron (II) or iron (III) oxides and / or iron ( II) and mixed oxides of iron (III). The iron oxide-containing charge may involve iron ores from which metallic iron can be economically extracted. These iron ores are typically rich in iron oxides in the following forms: magnetite (Fe 3O 4 , 72.4 wt.-% Fe), hematite (Fe 2O 3 , 69.9 wt.-% Fe), goethite ( FeO(OH), 62.9 wt.-% Fe), limonite (FeO(OH)·n(H 2O), 55 wt.-% Fe), or siderite (FeCO 3, 48.2 wt.-% Fe) . The iron oxide-containing charge may also contain direct reduced iron (sponge iron, DRI), hot brittle iron (HBI), scrap or mixtures thereof.

[0017] In the context disclosed herein, a recombinant plant is an ammonia reformer plant (also known as an ammonia cracking plant) and includes at least one reformer configured to recombine (i.e., crack) ammonia according to the following reaction: 2 NH 3 → N 2+ 3 H2. In other words, the reconstitution equipment is where the ammonia is cracked.

[0018] In specific examples, other reducing agents and / or carburizing agents and / or fuels and reducing gases or mixtures thereof are supplied to the shaft furnace.

[0019] In the context disclosed herein and in the case where the shaft furnace is a blast furnace, a typical reducing agent and carburizing agent is coking coal, which is loaded into the top of the blast furnace together with ferrous materials and materials injected at the tuyeres of the blast furnace. Materials such as pulverized coal, natural gas, coke oven gas, biogas, syngas, charcoal, etc.

[0020] In the context disclosed herein and in the case of a direct reduction furnace, typical reducing agents and carburizing agents are natural gas and synthesis gas (gas produced by the reformation of hydrocarbon-containing gases, such as natural gas, which mainly contain CO, H2 and A small amount of CH 4, N 2, H 2O, CO 2, etc.).

[0021] In a specific example, the ammonia recombinant equipment may include a plurality of recombiners arranged in series or in parallel with each other; or the ammonia recombinant equipment may include a plurality of recombiners arranged to form at least two recombiners in series, and the at least two recombiners may be arranged in series. The recombiners are connected in series and parallel to each other. In specific examples where the ammonia reformer apparatus contains more than one reformer, these reformers may be the same as or different from each other. In an ammonia reformer plant, the exact number, type and arrangement of the reformers can advantageously be adapted to the subsequent supply of the produced reducing gas to the shaft furnace in order to meet the requirements for the produced reducing gas (e.g. such as temperature, ammonia residual amount).

[0022] In another aspect, the present invention also proposes a shaft furnace equipment, which includes: shaft furnace; and Ammonia recombination equipment has a gas inlet and a gas outlet, the gas inlet is fluidly connected to an ammonia source and / or a heat exchanger, and the gas outlet is fluidly connected to a shaft furnace.

[0023] Advantageously, the shaft furnace apparatus is configured to operate by carrying out a method according to the first aspect, and as described in more detail below.

[0024] Therefore, this paper discloses an integrated approach and corresponding equipment that can operate a shaft furnace with reduced coking and / or other carbon source rates, a smaller CO2 footprint and optimal use of existing infrastructure.

[0025] This method proposes the use of ammonia as a novel, simple and economical energy carrier, ideally suited to the requirements of the steelmaking industry, and more specifically to shaft furnaces, with the aim of reducing CO2 emissions while maintaining most of the existing infrastructure.

[0026] In fact, the inventor of this case has found that this operating method is very suitable for the CO 2 lean energy strategy of various countries. The transport of ammonia can be achieved in very similar installations designed to transport liquefied natural gas (LNG) or liquefied petroleum gas (LPG). Existing infrastructure can also be adapted relatively easily because ammonia's liquefaction temperature is at ambient pressure. is -33°C. Therefore, this is compatible with typical LPG and / or LNG installations.

[0027] In order to reduce CO2 emissions from steel plants, ammonia can be used directly as an additional fuel gas in burners such as in thermal furnace plants, reheating furnaces, etc. and thermal power plants. When using ammonia directly in the burner, one faces NOx emission issues associated with the combustion of ammonia, a nitrogen-rich fuel. Such problems can be avoided when the cracked hot ammonia is supplied to the shaft furnace as reducing agent (ie as reducing gas) as described above. The remaining reducing gas leaving the shaft furnace will cause H2, H2O and N2 components to be added to the leaving top gas. After the H 2O is condensed, the leaving top gas will only be rich in N 2 and H 2 and will have minimal impact on the formation of NOx during its combustion. It even has a positive effect, i.e. the leaving top gas has an increased lower calorific value, leading to higher efficiency and therefore reduced energy consumption in downstream furnaces and thermal power plants using the top gas leaving the shaft furnace.

[0028] Therefore, the main benefit of the proposed approach is to identify a way to increase the efficiency of ammonia utilization in steel plants, and specifically in shaft furnaces, in order to further reduce CO2 emissions.

[0029] Another advantage is that the production of syngas with high hydrogen (H2) content from ammonia by the recombination (ie cracking) process is efficient.

[0030] In addition, the cracking of ammonia is a highly endothermic reaction, which requires a large amount of energy (i.e., approximately 2.5 MJ / Nm of NH) to proceed. Therefore, the injection of hot uncracked ammonia in the shaft furnace can be compared thermally with the injection of cold N and cold H, and will therefore significantly reduce the temperature at the injection point, thereby slowing down the interaction between the reducing gas and the iron oxide-containing charge. Reaction. More coking coal needs to be charged to compensate for the cooling effect produced by the injection of uncracked ammonia, thereby negatively impacting the CO2 reduction potential. Therefore, cracking ammonia outside the shaft furnace prevents the consumption of additional carbonaceous reducing agent to operate the shaft furnace, thereby reducing CO2 emissions of the shaft furnace equipment.

[0031] In addition, since the cracking of ammonia occurs outside the shaft furnace, the reaction can be better monitored and controlled, so that the operator always knows the composition of the reducing gas supplied to the shaft furnace (i.e. the amount of H2 and N2 and the possible the amount of residual NH3 reacted), allowing for better control of iron production.

[0032] In a specific example, the ammonia conversion rate 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, thus ensuring stable quality and characteristics of the reducing gas injected into the shaft furnace.

[0033] Alternatively, the reduction potential and other characteristics (such as temperature and pressure) of the reducing gas can be dynamically adjusted to meet changes in shaft furnace requirements. Such adjustments are of particular interest when the supply of iron oxide-containing charge is not constant over time, and / or when it is necessary to adjust the quality of the iron produced during production without having to stop the shaft furnace.

[0034] The main advantages and benefits of the operating method and shaft furnace device according to the invention can be summarized as follows: - Reuse of existing infrastructure; - Transport is cost-effective compared to hydrogen transport because ammonia has a higher energy density by volume than hydrogen; - Improve the efficiency of ammonia utilization in shaft furnace operation.

[0035] These and further advantages of the present method for operating a shaft furnace and the presently disclosed shaft furnace apparatus will be described in further detail below.

[0036] As mentioned above, the cleavage of ammonia proceeds according to the following reaction scheme: 2 NH 3 → N 2+ 3 H 2 . The cracking (i.e. recombination) of ammonia requires high activation energy, which makes the use of catalysts useful. At high temperatures, typically at the temperatures required for injection into the shaft furnace, such as about 700°C to 1000°C, ammonia decomposition (i.e. cracking or reforming) can also be carried out without the use of catalysts. However, non-catalytic reforming of ammonia may require a longer residence time of the ammonia in at least one reformer of the ammonia reforming plant, and thus a larger reformer will be required.

[0037] Thus, the reorganization (i.e., cleavage) of ammonia can be performed catalytically or non-catalytically.

[0038] Additionally, the use of a catalyst will provide the endotherm required for ammonia decomposition (i.e., recombination or cracking) at lower temperatures. This is particularly important because cracking (i.e., recombination) requires very high energy, similar to that required to heat ammonia from ambient temperature to approximately 1000°C. Therefore, performing the recombination step at a relatively low temperature, i.e. below about 900°C or even below about 700°C will help to increase the thermal efficiency of the process. Therefore, in a specific example, the cracking of ammonia in an ammonia reforming plant is advantageously carried out catalytically to produce a reducing gas stream.

[0039] Today, the development of catalysts for ammonia cracking (i.e. ammonia reforming) is still ongoing. Any kind of catalyst may be used in the present process, for example such as a nickel-based catalyst or any catalyst that operates at high temperatures, ie at temperatures up to about 1000°C. However, the use of catalysts operating at temperatures close to possible thermodynamic temperatures, i.e. at high conversions of ammonia of about 500°C, can be advantageously used in the reformer to increase its thermal efficiency.

[0040] Advantageously, the ammonia conversion during the recombination process should be as high as possible, since this means a higher concentration of hydrogen H2 in the reducing gas and a lower concentration of residual ammonia NH3. This is particularly important because the decomposition of ammonia is endothermic and therefore cools the atmosphere inside the shaft furnace and thus has a negative impact on shaft furnace production. In fact, reducing gas with 10 mol-% ammonia reduces its temperature by about 40°C when converting ammonia adiabatically.

[0041] The inventor of this case surprisingly found that when operating the shaft furnace equipment in this method, there is no problem with residual ammonia in the reducing gas, and there is no need to carry out ammonia recombination (i.e. cracking) at low temperature. This is because the resulting reducing gas A high temperature is required, generally above 800°C, to allow it to be injected into the shaft furnace.

[0042] As mentioned above, the reducing gas may contain ammonia, ie, uncracked (or unrecombined) ammonia. Depending on the requirements of the shaft furnace, the reducing gas may contain varying degrees of residual ammonia, such as less than 15 mol-% ammonia, less than 10 mol-% ammonia or even less than 5 mol-% ammonia. Since the ammonia reformation method does not need to be completed, efficient use of ammonia in the shaft furnace to reduce the CO2 footprint is an easy benefit.

[0043] Preferably, the temperature of the recombination process, ie the temperature at which the ammonia is cracked, may substantially correspond to the temperature at which the reducing gas is supplied to the shaft furnace.

[0044] Preferably, the pressure of the reforming method, ie the pressure at which cracking is carried out, corresponds to the pressure at the neck height of the blast furnace plus the pressure losses in the pipes and the reformer. Typical pressure levels at the inlet of the reforming plant will be below about 15 barg, more specifically below 12 barg.

[0045] Advantageously, the ammonia reforming plant may comprise a heat exchanger arranged so that cooling energy is supplied to users in the steel plant, such as room air conditioning, cooling water cooling, etc., and the cooling energy is supplied from the ammonia storage device to At least one reformer is produced by heating and possibly evaporating an ammonia stream.

[0046] Alternatively and / or in addition, the ammonia is heated in a heat exchanger with flue gas from the ammonia reformer and / or with flue gas from the combustion of a fuel gas specifically used for this purpose before entering the reformer.

[0047] Heat exchangers can be of different types, such as tube bundle type, plate heat exchanger, etc.

[0048] In a preferred embodiment, the method further includes the steps of collecting the top gas flow from the shaft furnace and burning the top gas flow in a burner of the ammonia reforming unit. In this context, top gas refers to the gas exiting at the top of the shaft furnace, such as blast furnace gas in the specific example where the shaft furnace is a blast furnace, and may also be referred to as shaft furnace gas. Alternatively or in addition, steel plant gases, ammonia itself and / or biofuels such as biomass, biomass, etc. or mixtures thereof may be used in the burners of the ammonia reforming plant.

[0049] As mentioned above, the heating and cracking (i.e., recombination) of ammonia consumes a large amount of energy. Heating gaseous ammonia at about 25°C to 950°C and reforming (i.e. cracking) it into hydrogen H and nitrogen N requires about 4.5 MJ / Nm of ammonia NH. Advantageously, this energy can be supplied by burning the top gas from the shaft furnace in the burner of the ammonia reforming plant, thus allowing the energy of the shaft furnace gas to be recycled directly to the shaft furnace for metallurgical reasons instead of making it useful for electrical energy production with low energy efficiency. Further CO2 emissions reductions can be achieved using the method of operating a shaft furnace plant according to the invention since no additional carbonaceous fuel gas has to be burned in the burners of the recombinant plant. Alternatively or in addition, steel plant gases, ammonia itself and / or biofuels such as biomass, biomass, etc. or mixtures thereof are used in the burners of the ammonia reforming plant.

[0050] According to a preferred embodiment, the reducing gas is supplied directly through the neck of the shaft furnace. In the specific example where the shaft furnace is a direct reduction reactor, this means that the reducing gas is preferably injected into the reduction zone of the reactor, ie neither into the throat nor into the cooling zone. In the specific case where the shaft furnace is a blast furnace, this means that the reducing gas can be injected at the height of the furnace neck, that is, above the height of the hot blast, preferably in the gas-solid reduction zone of ferrous oxide above the bonding zone. Injection of the produced reducing gas at the neck level of the blast furnace significantly reduces the coking rate, i.e. the amount of coking coal and / or other carbon sources produced per ton of pig iron.

[0051] Alternatively or in addition, the reducing gas can be supplied at the tuyere height of the blast furnace, preferably at a high temperature after cracking. Although the injection of reducing gas through the tuyere increases the oxygen requirements of the blast furnace operation and thereby generally reduces the possibility of auxiliary fuel addition, reducing gas containing cracked ammonia can advantageously be injected at high temperatures after cracking at the height of the tuyere, with or without addition Add O2 to heat to flame temperature in the tank plate, or with or without plasma heating to reach flame temperature outside the furnace. Therefore, reducing gas containing cracked ammonia can be injected at the height of the tuyere, and (reducing) gas can be injected or not injected at the lower furnace neck. In addition, at the upper height of the furnace neck of the recirculating and cooling (condensing) shaft furnace top gas, the reducing gas containing cracked ammonia can be injected at the height of the tuyere or not. The reducing gas containing cracked ammonia has previously been directly and / or Or indirect heating to 700 to 1000°C.

[0052] In a preferred embodiment, in addition to the reducing gas injected at the neck of the blast furnace, auxiliary fuel is also supplied to the blast furnace. The auxiliary fuel may advantageously be pulverized coal, natural gas, coke oven gas and / or hydrogen. The injection of reducing gas into the furnace neck of the shaft furnace and in particular of the blast furnace allows the injection of pulverized coal, natural gas and in particular hydrogen or other materials from higher tuyeres. In fact, the neck injection (or supply) of cracked ammonia as reducing gas increases the top gas temperature, thereby allowing higher oxygen enrichment at the tuyere height, and therefore higher auxiliary fuel injection, such as PCI, NG, COG and hydrogen. As mentioned above, cracked ammonia and / or ammonia-containing reducing gas (as auxiliary fuel) can also be added at the height of the tuyere, with or without O 2 , with or without additional plasma heating, and injected at the lower furnace neck. Or no reducing gas is injected. Excess coking coal can therefore be replaced by hydrogen-rich auxiliary fuel, allowing a further reduction in the carbon content of the blast furnace reductant (i.e. lowering the amount of coking coal required) and thus reducing CO2 emissions.

[0053] According to some specific examples, in addition to the reducing gas, a synthesis gas stream is also supplied to the shaft furnace. In such specific examples, iron reduction is also produced by the reaction between the synthesis gas stream and the iron oxide-containing charge.

[0054] The synthesis gas stream may advantageously be produced by reforming industrial gases (for example such as shaft furnace top gas, steam and / or basic oxygen furnace gas) and fuel gases (for example such as coke oven gas, natural gas, methane and / or biogas) Production.

[0055] According to the same or alternative embodiments, HBI and / or scrap may be fed to the blast furnace as part of the iron oxide-containing charge.

[0056] HBI is an interesting form of energy transport because it combines ease of transport with high energy density. In fact, HBI's compressed form facilitates its handling and transportation, so it can be transported using existing infrastructure. HBI is compressed direct reduced iron, that is, pretreated iron ore. The transportation of HBI advantageously combines the transportation of raw materials supplied as iron oxide-containing charge in the blast furnace with the transportation of energy, while avoiding unreduced ore. Combined oxygen transport. In fact, since HBI is pre-treated iron ore, less energy is required to obtain fully processed iron in the blast furnace, as HBI already has a high content of metallic iron.

[0057] In order to achieve important CO2 emission reductions, HBI is preferably produced from green hydrogen. Alternatively, it can be produced from natural gas by applying carbon capture to hydrogen and / or DRI production methods.

[0058] Another advantage of HBI loaded into blast furnaces is that relatively low grade ores can be used to manufacture HBI. This is because HBI will be melted in the blast furnace and the iron and slag will be separated in the blast furnace as usual. Therefore, lower quality raw materials can be used resulting in higher blast furnace slag formation rates and higher impurities, such as HBI required for electric steelmaking using electric arc furnace (EAF) technology. In other words, HBI of insufficient quality for use in EAF technology is advantageously used as part of the iron oxide-containing charge to be fed into the blast furnace, thereby further reducing the energy consumption of the shaft furnace equipment and its CO2 emissions.

[0059] Additionally, as mentioned above, feeding cracked (or reformed) ammonia as a reducing gas into the blast furnace results in a higher temperature of the top gas leaving the blast furnace. This higher top gas temperature allows the use of more HBI as charge compared to a blast furnace not operated according to the present method (i.e. without injection of cracked ammonia).

[0060] At high HBI loading rates, high CO2 emission reductions can be achieved. CO2 emission reduction can also be achieved using CO2 lean auxiliary fuel, such as COG. However, when CO2 lean auxiliary fuels (such as COG) are used with HBI, traditional blast furnace operating methods quickly reach their limits and do not result in CO2 emission reductions using HBI (and loading) on ​​one hand and HBI on the other. The total emission reductions that can be achieved using CO2 lean auxiliary fuel. In fact, charging the blast furnace with HBI and using CO2 lean auxiliary fuel both reduce the top gas temperature of the blast furnace, so the combination of the two method improvements (HBI charging and using CO2 lean auxiliary fuel) is not allowed to achieve the respective to the greatest extent.

[0061] Optimal CO reduction is achieved when the injection of CO2 lean gas fuel through the tuyere of the blast furnace is combined with the HBI charging of the blast furnace and the furnace neck injection of thermal reducing gases such as ammonia cracking products (i.e. cracked or recombinant ammonia). This is because the neck injection of reducing gas beneficially increases the top gas temperature of the blast furnace, thereby balancing the cooling effect of the HBI charge and the use of CO 2 lean gas fuel. In a particularly preferred embodiment, cracked (i.e. recombinant) ammonia is used in a blast furnace as a supply of reducing gas and auxiliary fuel, for example as a supply of coke oven gas (COG), and as a supply of oxidized gas to be melted in the blast furnace. The iron part of the charge is combined with the supply of HBI. According to this specific example, neck injection to produce recombinant ammonia at a higher blast furnace top gas temperature can achieve higher HBI and COG rates due to higher top gas temperatures, and therefore result in lower CO2 emissions, specifically A CO2 emission reduction of up to approximately 38% can be observed, as well as a significant productivity increase.

[0062] The term "fluid connection" means that two devices are connected by a conduit or pipe so that fluid (such as gas) can flow from one device to another. This expression includes means for changing this flow, such as valves or fans for regulating mass flow, compressors for regulating pressure, etc., as well as control elements, such as for the operation of the shaft furnace as a whole or for each individual unit within the shaft furnace equipment. Sensors, actuators, etc. necessary or desired for proper control of the operation of the element.

[0063] As used herein, "recombinant" refers to any container, vessel, etc., in which a recombination process can be performed, such as a recombinant reactor or a recombinant vessel.

[0064] "Supply to the furnace neck", "Inject into the furnace neck", "Supply to the furnace neck", "Supply at the furnace neck height...", "Supply through the furnace neck...", "Supply at the furnace neck height" or " "Injecting at neck height" means injecting material (for example such as gas) directly into the neck of the shaft furnace. In the specific example where the shaft furnace is a blast furnace, this means that the material is injected into the gas-solid reduction zone of ferrous oxide above the height of the hot blast, that is, above the furnace belly, preferably above the bonding zone in the blast furnace.

[0065] In this article, "supply to the shaft furnace" and "inject into the shaft furnace" and "supply into the shaft furnace" and "inject into the shaft furnace" or "inject into the shaft furnace" are used synonymously and have the same meaning respectively. This means Instructs material to be poured into the shaft furnace.

[0066] "About" in the context of the present invention means that a given value relates to a range of values ​​from -10% to +10% of that value, preferably from -5% to +5% of that value. Unless otherwise stated, all percentages relating to elemental and molecular proportions herein are expressed as wt.-%, except for gaseous components, where proportions are expressed as mol-%.

[0067] Further details and advantages disclosed herein will become apparent from the following detailed description of several non-limiting specific examples with reference to the accompanying drawings. Simple explanation of the diagram

[0068] Preferred specific examples disclosed herein will now be described by way of example with reference to the accompanying drawings, in which: [Fig. 1] is a schematic diagram of a specific example of a first variant of shaft furnace equipment configured to implement the present shaft furnace operating method; and [Fig. 2] is a schematic diagram of a specific example of a second variation of shaft furnace equipment configured to implement the present shaft furnace operating method. Implementation

[0069] Below, two different variants of the method for operating the furnace neck and shaft furnace equipment are shown in conjunction with the figures.

[0070] Figure 1 shows a specific example of a first embodiment of the present method for operating a shaft furnace, which includes reforming (i.e. cracking) ammonia to produce a first reducing gas stream (i.e. cracking ammonia), and injecting the first reducing gas stream through The neck of the shaft furnace.

[0071] As schematically shown in FIG. 1 , the shaft furnace equipment 10 includes a shaft furnace 12 and a reforming equipment 14 including an ammonia reformer fluidly connected to the shaft furnace 12 . At the top, the shaft furnace 12 generally receives a charge 16 containing iron oxide. At the bottom of the shaft furnace 12, the reduced iron and slag products 18 are taken out.

[0072] Auxiliary fuel 30 may be injected into the lower part of shaft furnace 12 . The auxiliary fuel may comprise coke oven gas, natural gas, or any other gas commonly used as an auxiliary fuel for operating a shaft furnace.

[0073] At the top, the shaft furnace gas 32 leaving the shaft furnace 12 is recovered. The recovered shaft furnace gas 32 is generally pretreated upon exiting the shaft furnace 12 . The pretreatment of the shaft furnace gas 32 involves first cooling to reduce its vapor content, followed by cleaning, in particular the removal of dust and / or HCl and / or metallic compounds. In the specific example of FIG. 1 , the cooling and cleaning of the shaft furnace gas 32 occurs in the cooling and cleaning unit 34 .

[0074] Downstream of the cooling and cleaning unit 34, the shaft furnace gas flow is divided into at least two flows. One stream is called shaft furnace output gas 36 and can be fed to another unit of the plant containing the present 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 necessary energy to carry out the reforming (i.e., cracking) of ammonia.

[0075] Alternatively or in addition, a portion of the shaft furnace gases may be diverted to a separate unit (such as heat exchanger 42) and then injected into the burners of shaft furnace 12 and / or reformer 44.

[0076] Another portion of the shaft furnace gas may be introduced directly into the ammonia reformer 14 via conduits 48 and 22.

[0077] Shaft furnace gas (SFG) contains up to approximately 40% of the energy input to the shaft furnace. In order to reduce the CO2 footprint of shaft furnace-based metal (iron) production, an important strategy is to make this SFG available for as many metallurgical purposes as possible. Therefore, the reforming or cracking of ammonia for the production of reducing gas should use as much shaft furnace gas as possible in order to increase the CO2 emission reduction potential of shaft furnace metal manufacturing.

[0078] At the height of the furnace neck, the shaft furnace 12 receives reducing gas 20 . The reducing gas 20 reacts with the iron oxide-containing charge 16 in the shaft furnace 12 to produce reduced iron oxide and metallic iron. The DRI 18 will be removed from the underside of the stove. According to a specific example of the invention, the reducing gas 20 is produced in the reforming device 14, that is, in an ammonia reformer. The reducing gas 20 is cracked ammonia 22 and contains N 2 and H 2 . The recombination process occurs according to the following reactions: 2NH 3→ N 2+ 3 H 2.

[0079] This can be maintained by high temperatures inside the ammonia reformer and / or by the use of a catalyst such as, for example, a nickel-based catalyst or any catalyst operating 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 in fluid connection with the reformer. In this particular configuration, ammonia is passed from storage tank 24 through heat exchanger 46 to heat the ammonia to ambient temperature.

[0080] Turning now to Figure 2, a second specific example of the present shaft furnace apparatus 10 and its method of operation is shown. In this specific example, the shaft furnace is a blast furnace 112.

[0081] At its top, the blast furnace 112 generally receives coking coal (not shown) and ore from the bunker. The ore is generally referred to as the iron oxide-containing charge 16. According to embodiments of the present invention, HBI 116 may also be supplied to the top of blast furnace 112 as part of the iron oxide-containing charge 16 to be melted therein.

[0082] At the bottom of the blast furnace 112, liquid pig iron and slag (i.e. iron product) 18 are taken out. The operation of the blast furnace 112 itself is well known and will not be described further herein.

[0083] At the lower part of the blast furnace 112 , that is, at the height of the tuyere, the blast furnace receives hot air 26 provided by a hot blast furnace device 28 including a plurality of cowpers and auxiliary fuel 30 . Hot air 26 may contain air or oxygen-rich gas. The auxiliary 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 an auxiliary fuel for operating a blast furnace.

[0084] The blast furnace 112 receives the reducing gas 20 at the furnace neck height above the tuyere level. According to a specific example of the invention, the reducing gas 20 is produced in the reforming device 14, that is, in an ammonia reformer. The reducing gas is cracked ammonia 22 and contains N 2 and H 2 . The ammonia reformer contains at least a burner 40 supplied with fuel gas.

[0085] Reducing gas 20 with a high hydrogen content is injected into the blast furnace 112 at the height of the furnace neck.

[0086] At the top, blast furnace gas 32 exiting blast furnace 112 is recovered. The recovered blast furnace gas 32 is generally pretreated upon exiting the blast furnace 112 . Pretreatment of the blast furnace gas 32 involves first cooling to reduce its vapor content, followed by cleaning, in particular the removal of dust and / or HCl and / or metallic compounds. In the specific example of Figure 2, the cooling and cleaning of the blast furnace gases takes place in the cooling and cleaning unit 34. Alternatively, separate units may be used: a first unit performs cooling and a second unit (or second units) performs cleaning, or vice versa.

[0087] Downstream of the cooling and cleaning unit 34, the blast furnace gas flow is divided into at least two flows. One stream is called blast furnace output gas 36 and can be fed to another unit of the steelmaking plant containing the present 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 necessary energy to carry out the reforming (i.e., cracking) of ammonia.

[0088] Blast furnace gas (BFG) contains up to approximately 40% of the energy input to the blast furnace. To reduce the CO2 footprint of blast furnace-based steel production, an important strategy is to make this BFG available for as many metallurgical purposes as possible. Therefore, the recombination or cracking of ammonia for the production of reducing gas should use as much blast furnace gas as possible in order to increase the CO2 emission reduction potential of blast furnace ironmaking.

[0089] A shaft furnace apparatus 10 as described above with reference to Figure 2 may operate according to the methods described herein to produce iron. Table 1 is a comparison of conventional operation of a blast furnace (reference case) and operation of a blast furnace with injection of cracked ammonia (i.e. first reducing gas stream) according to three specific examples of the present process. [Table 1] project unit Reference situation Scenario 1: Cracking ammonia injection Case 2: cracked ammonia injection + COG injection Situation 3: cracked ammonia injection + COG injection + HBI [Drying rate] [(] [per ton of molten iron] [)] HBI kg / t 0 0 0 407 Total coking rate kg / t 301 220 202 201 Coal injection rate kg / t 192 192 181 91 COG injected into the tuyere Nm 3 / t 0 0 115 135 Furnace neck injection cracked ammonia Nm 3 / t 0 400 400 400 [Blast conditions] Natural drying blast volume Nm 3 / tHM 830 744 412 381 Oxygen-enriched Nm 3 / tHM 63 50 130 97 flame temperature °C 2239 2162 2149 2126 [stove top gas] CO mol-% 24.32 18.6 20.5 22.1 CO 2 mol-% 24.22 18.8 21.7 12.8 H 2 mol-% 3.8 15.1 22.8 29.7 N 2 mol-% 47.7 47.6 34.9 35.4 temperature °C 125 220 169 162 Volume (dry) Nm 3 / tHM 1401 1455 1268 1187 Low calorific value (dry) kJ / Nm 3 3479 3969 5056 5997 [CO, 2 , ] CO2 emissions kg / tHM 1973 1634 1528 1221 CO2 emissions reduction (relative to reference case) % 17 twenty three 38

[0090] For the calculation of CO2 emissions under different circumstances, the following emission factors are considered for different input materials (Table 2). [Table 2] [Material] [CO, 2 , ] [Emissions] coking coal 4.17 kgCO2 / kg Pulverized coal 2.79 kgCO2 / kg Sinter 0.196 kgCO2 / kg HBI 0kgCO2 / kg* COG 0kgCO2 / Nm3 BFG output 0kgCO 2 / Nm 3**

[0091] *Typically, there is some carbon (about 1.5 wt.-%) in HBI. In this case, green HBI, which has been produced without carbon, is used.

[0092] **CO2 emissions have been attributed to molten iron

[0093] In the reference operation, the blast furnace is injected with coking coal and pulverized coal only at the tuyere, while in case 1, cracked ammonia is additionally injected at the neck height of the blast furnace (i.e. through the neck). It can be seen from case 1 that by injecting 400 Nm 3 / tHM (Nm 3 / t molten iron) of cracked ammonia through the furnace neck, the coking rate can be significantly reduced from 301 (as reference) to 220 kg / tHM (case 1). CO 2 emissions have been reduced from 1973 (as a reference) to 1634 kg / tHM (case 1), resulting in a 17% reduction in CO 2 emissions. The rate expressed as " / tHM" relates to each ton (metric tons) of hot metal produced by the shaft furnace. "Nm 3" refers to the standard cubic meter, which represents the volume of 1 cubic meter of gas under normal conditions, that is, at a temperature of 0°C (273.15K) and an absolute pressure of 1 atm (101.325 kPa).

[0094] In case 2 (Table 1), cracked ammonia is injected at the neck height of the blast furnace (as in case 1), and coke oven gas (COG) is injected through the tuyere of the blast furnace. When the injection of auxiliary fuel (such as COG) is increased, the enrichment of oxygen must be increased in order to maintain the flame temperature. Flame temperatures are typically higher than 2000°C when using PCI, and higher than 1800°C when not using PCI.

[0095] Increasing oxygen enrichment in a blast furnace means reducing the amount of natural blast (air) that will be used in the blast furnace. Therefore, the total amount of hot air entering the blast furnace is reduced from 830 (as reference) to 412 Nm3 / tHM (case 2).

[0096] From Case 2 of Table 1, it can be seen that simultaneous injection of COG and pulverized coal is possible and allows a sufficient top gas temperature of approximately 169°C. COG injection can further reduce the coking rate from 220 (case 1) to 202 kg / tHM (case 2). Therefore, the associated CO2 emissions are reduced from 1634 (case 1) to 1528 kg / tHM (case 2), which is equivalent to an additional 6% reduction in CO2 emissions. Relative to the reference case, CO2 emissions in Case 2 are reduced by 23%.

[0097] In the last case shown in Table 1 (case 3), in addition to the injection of cracked ammonia and COG, HBI is also supplied as part of the iron oxide-containing charge. Supplying HBI reduces the coal rate (i.e. pulverized coal injection rate) while maintaining essentially the same coking rate relative to Case 2 (202 vs. 201 kg / tHM), which is expected and equivalent to the minimum coking rate for which the blast furnace is operable, This ensures the required permeability of the gas-solid-liquid reactor. It can be seen that the CO2 footprint is further reduced due to the reduction in overall carbon input. CO2 emissions are only 1221 kg / tHM, which corresponds to a 38% reduction in CO2 emissions compared to the reference case.

[0098] When reading Table 1, it can be seen that replacing some coking coal with cracked ammonia increases the lower calorific value of the top gas, thereby allowing for increased efficiency in the downstream utilization of top gas (i.e. blast furnace gas) in power plants and / or other furnaces. By injecting coke oven gas (COG) as an auxiliary fuel and / or injecting HBI as a charge containing iron oxide to further reduce the coking rate, the low calorific value of the top gas is further improved.

[0099] While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary rather than restrictive; the invention is not limited to the specific examples disclosed. Those with ordinary knowledge in the technical field to which the present invention belongs can understand and realize other changes to the specific examples disclosed when practicing the claimed invention by studying the drawings, the disclosure content and the appended patent application scope.

[0100] 10: Shaft furnace equipment 12: Shaft furnace 14: Ammonia reformer equipment / recombiner 16: Charge containing iron oxide 18: Iron products 20: Reducing gas 22: Ammonia NH 3 24: Ammonia NH 3 storage tank 26:Hot air 28:Hot blast stove equipment 30: Auxiliary fuel 32: Blast furnace gas 34: Cooling and cleaning unit 36: Output gas 38: Pretreated blast furnace gas 40:Burner 42:Heat exchanger 44:Reorganizer 46:Heat exchanger 48:Catheter 112:blast furnace 116: Hot pressed iron (HBI)

Claims

1. A method for operating a blast furnace apparatus (10) comprising a blast furnace (112) and an ammonia reforming unit (14), the method comprising the steps of: a. supplying an ammonia stream (22) to the ammonia reforming unit (14); b. cracking the ammonia stream (22) in the ammonia reforming unit (14) to produce a reducing gas (20); c. supplying an iron oxide-containing charge (16) and the reducing gas (20) to the blast furnace (112); d. reducing iron oxide inside the blast furnace (112) by a reaction between the iron oxide-containing charge (16) and the reducing gas (20), wherein the reducing gas (20) contains less than 15% ammonia, preferably less than 10% ammonia.

2. The method of claim 1, wherein the pyrolysis in step b) is carried out in a catalytic manner.

3. The method of claim 1, further comprising the step of collecting the top gas flow (32) from the blast furnace (112) and burning the top gas flow in the burner (40) of the ammonia reforming unit (14).

4. The method of any one of claims 1 to 3, further comprising the step of supplying other reducing agents and / or carburizing agents and / or fuel, as well as the reducing gas or a mixture thereof, to the blast furnace.

5. The method of any one of claims 1 to 3, wherein steel mill gas, ammonia itself and / or biofuel, such as biogas, biomass or mixtures thereof, are used in the burner (40) of the ammonia reforming unit (14).

6. The method of any one of claims 1 to 3, wherein the energy used for heating and / or evaporating ammonia to ambient temperature is used to meet the cooling needs of the steel plant, such as air conditioning and / or cooling water cooling.

7. The method of any one of claims 1 to 3, wherein the blast furnace includes a neck and the supply of the reducing gas (20) is carried out directly through the neck of the blast furnace (112).

8. The method of any one of claims 1 to 3, wherein in addition to the reducing gas (20), auxiliary fuel, reducing agent and / or carburizing agent (30) are also supplied to the blast furnace (112).

9. The method of claim 8, wherein the auxiliary fuel (30) is pulverized coal, natural gas, coke oven gas, biogas, syngas, ammonia, cracked ammonia, hydrogen and / or mixtures thereof supplied to the blast furnace at the tuyer height.

10. The method of any one of claims 1 to 3, wherein in addition to the reducing gas (20), a synthesis gas stream is also supplied to the blast furnace (112), and wherein iron products are also produced by the reaction between the synthesis gas stream and the iron oxide-containing charge (16).

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

12. The method of claim 11, wherein hot press iron (HBI) (116) and / or scrap are supplied to the blast furnace (112) as part of the iron oxide-containing charge (16).

13. A blast furnace apparatus (10) configured to implement the method of any one of claims 1 to 12, the blast furnace apparatus comprising: a blast furnace (112); and an ammonia reforming apparatus (14) having a gas inlet and a gas outlet, the gas inlet being fluidly connected to an ammonia source (24) and / or a heat exchanger, and the gas outlet being fluidly connected to the blast furnace (112).

14. The blast furnace equipment (10) of claim 13, wherein the top of the blast furnace is fluidly connected to the burner (40) of the ammonia reforming equipment (14).

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