Method for operating smelting furnace installation

Abstract

A method for operating a smelting furnace installation, in particular a blast furnace installation, comprising:-feeding coke, iron-containing oxide material and, if necessary, flux to the furnace top of the smelting furnace,-injecting a first reducing gas containing hydrogen at the tuyere level of the smelting furnace at a temperature higher than 1600 DEG C, a first reducing gas is injected at the lower shaft level of the smelting furnace, oxygen is injected at the tuyere level of the smelting furnace, and a second reducing gas is injected at the lower shaft level of the smelting furnace, the coke is fed at a lump coke ratio of less than 220 kg / t HM, preferably less than 200 kg / t HM and more preferably less than 180 kg / t HM, and the flow rate of oxygen injected at the tuyere level is less than 120 Nm3 / t HM, preferably less than 112 Nm3 / t HM.

Description

Technical Field

[0001] The present invention generally relates to a method for operating a smelting furnace facility, in particular a blast furnace facility, and also to the smelting furnace facility or blast furnace facility. Background Art

[0002] One of the main issues facing smelting furnace facilities today is their CO 2 emissions, which seem inevitably associated with the operation of such smelters / blast furnaces. On the contrary, steel production is a key factor in reducing these emissions, as it generates CO 2 The construction of emission reduction technology provides raw materials.

[0003] Although alternative methods and facilities exist (eg scrap melting or direct reduction process followed by melting in an electric arc furnace), smelting furnaces (ie reduction and melting furnaces) such as blast furnaces (BF) are still today the most widely used process in steel production.

[0004] In fact, blast furnaces have a long tradition in iron and steel making, thanks to their wide range of uses, mainly in utilizing a variety of iron-containing materials. The disadvantage of blast furnaces lies in the fact that they use large amounts of carbon brought by coke and / or auxiliary fuels to reduce the ore and provide high flame temperatures of >1800°C to supply the energy required to reduce, heat and melt the iron and gangue.

[0005] Furthermore, coke is a solid matrix in the furnace to allow adequate permeability in the lower part of the furnace, where the partially reduced iron ore is heated to melting temperature and then melted in the so-called soft melting zone. In the soft melting zone, the ore material softens and loses most of its permeability. Therefore, in the soft melting zone, the gas mainly flows through the coke layer arranged in this zone. Below the soft melting zone is the dripping zone, in which the molten material drips downwards in a countercurrent / crosscurrent manner to the rising reducing gas flow. In order for this to happen correctly in both zones, the force exerted by the upstream gas on the downward flowing droplets must be within certain operating conditions.

[0006] Today, the minimum coke rate in a blast furnace is considered to be about 220 kg / t HM. This limitation is not due to process reasons but rather to the mechanical and / or fluid dynamic limitations mentioned above.

[0007] In fact, proposals to reduce the coke ratio to less than 100 kg / t HM were made many years ago. However, the steel industry has never adopted this extremely low coke ratio process proposal because many problems must be overcome if such a low coke ratio is to be truly achieved.

[0008] In fact, these problems may occur in different zones of a smelting furnace, such as, in particular, a blast furnace.

[0009] For example, in an ironmaking blast furnace, iron-containing oxide materials descend through the furnace, undergoing a process of reduction, softening, melting and dripping onto the hearth. At temperatures between the onset of softening and complete melting, they form a soft melting zone. In this soft melting zone, the passage volume of the rising gas becomes problematic when a reduced coke ratio is used. The reason is that the relative thickness of the ore layer increases, while the number of coke layers in the soft melting zone decreases. This in turn increases the gas velocity, which in turn increases the pressure drop in the soft melting zone.

[0010] As the velocity of the rising gas in the soft melting zone increases, the rising gas tends to diffuse horizontally toward the wall region and flow upward in the wall region following the path of least resistance. This adverse effect, known as the wall channeling phenomenon, results in heat loss and preferential gas flow through the charge, thereby causing uneven reduction and temperature of the charge, leading to severe operational disturbances.

[0011] Furthermore, the increase in gas velocity in the bosh may prevent the liquid metal and slag from flowing downward inside the drip zone, thereby causing an overflow phenomenon.

[0012] In the shaft of a blast furnace, reducing the coke ratio to very low values ​​has a significant impact on the void space of the solid charge. Due to the small size of the iron ore particles and the wide size distribution, the void space formed by the iron ore particles is smaller than that of the larger coke particles. The void space created between the coke particles is about 50%, while the average void space of the iron ore particles is only about 35%. In the case of very low coke ratios, the proportion of ore particles will be very high, so the void space in the shaft will be significantly reduced, resulting in a high gas pressure drop in the shaft. This may lead to the so-called hanging phenomenon, in which the charge materials do not move continuously downwards and they encounter very high resistance (very high gas pressure drop).

[0013] Finally, a minimum coke ratio is required to ensure proper carburization of the hot metal. In fact, keeping the carbon content stable is an important prerequisite to ensure the further transformation of iron into steel. Summary of the invention

[0014] Technical issues

[0015] The object of the present invention is to provide a method for operating a smelting furnace facility, in particular a blast furnace facility, which method can significantly reduce CO 2 emissions, while being able to appropriately address the above issues.

[0016] General Description of the Invention

[0017] In order to overcome the above problems, in a first aspect, the present invention provides a method for operating a smelting furnace (shaft furnace) facility (such as a blast furnace facility), wherein the method comprises the following steps:

[0018] - supplying coke, iron-containing oxides and other iron-containing materials (such as iron ore, hot briquetted iron (HBI), scrap, etc.) and, if necessary, flux to the top of the smelting furnace,

[0019] - injecting a first reducing gas containing hydrogen at a temperature above 1600°C at the tuyere level of the smelting furnace,

[0020] - injecting oxygen at the tuyere level of the smelting furnace, preferably at a temperature below 600°C, more preferably below 400°C, and

[0021] - Injection of a second reducing gas into the lower shaft of the smelting furnace at level.

[0022] According to the present invention, coke is supplied at a lump coke ratio of less than about 220 kg / t HM (such as less than about 200 kg / t HM, less than about 180 kg / t HM, less than about 160 kg / t HM, less than about 150 kg / t HM or less than about 140 kg / t HM) and most preferably less than about 130 kg / t HM, and wherein the oxygen flow rate injected at the tuyere level is less than about 120 Nm 3 / t HM, preferably less than about 112Nm 3 / t HM and more preferably less than about 100 Nm 3 / t HM (such as less than about 80Nm 3 / t HM, 40Nm 3 / t HM or even 20Nm 3 / t HM).

[0023] In a second aspect, the present invention provides a smelting furnace facility, in particular a blast furnace facility, comprising:

[0024] a charging device configured for feeding coke, iron-containing oxides and other iron-containing materials (such as iron ore, hot briquetted iron (HBI), scrap, etc.) and, if necessary, fluxes to the roof of the smelting furnace,

[0025] a first injector device, located at the tuyere level of the smelting furnace and configured for injecting a first reducing gas containing hydrogen at a temperature above 1600° C. at said tuyere level of the smelting furnace,

[0026] - a second injector device, located at the level of the shaft of the smelting furnace and configured for injecting a second reducing gas at the level of the lower shaft of the smelting furnace,

[0027] - oxygen injection port means, configured for injecting oxygen at the tuyere level of the smelting furnace,

[0028] wherein the charging device is configured to supply coke at a lump coke ratio of about 220 kg / t HM (such as less than about 200 kg / t HM, less than about 180 kg / t HM, less than about 160 kg / t HM, less than about 150 kg / t HM or less than about 140 kg / t HM) and most preferably less than about 130 kg / t HM; wherein the first injector device comprises an electric heating device configured to heat the first reducing gas to the above-mentioned temperature of more than 1600° C., and wherein the oxygen injection port is configured to inject the first reducing gas at a rate of less than 120 Nm 3 / t HM, preferably less than 112Nm 3 / t HM, more preferably less than 100Nm 3 / tHM (such as less than about 80Nm 3 / t HM, 40Nm 3 / t HM or even below about 20Nm 3 Therefore, the smelting furnace facility is preferably suitable for and configured to implement the method according to the first aspect.

[0029] Based on the premise that a significant reduction in the coke ratio will lead to a decrease in the permeability of the soft melting zone, the inventors designed a method of reducing the permeability of the soft melting zone by introducing a Figure 3 In principle, the reducing gas (i.e., the first reducing gas, Figure 3 The actual flow rate of the reducing gas (A) in the figure is reduced, thereby also reducing the velocity of the reducing gas. Since both the velocity and volume flow of the bosh gas are reduced, the upward force exerted on the slag and iron droplets is also reduced, thereby reducing the risk of overflow. However, although it seems ideal to reduce the amount of oxygen injected at the level of the tuyere in order to burn as little coke as possible, doing so will have a huge impact on the operation of the smelting furnace. In fact, an important feature of conventionally operated smelting furnaces / blast furnaces is that there must be a raceway at the level of the tuyere, that is, in a blast furnace operated with oxygen-containing hot blast, there is such a void space in front of the tuyere, the role of which is to properly distribute the gas in the blast furnace bosh. In conventionally operated furnaces, these raceways are formed by burning coke under the action of hot blast near the tuyere. It is generally recognized that reducing the oxygen flow injected at the level of the tuyere to such a low flow rate may inevitably hinder the normal operation of the furnace due to improper gas distribution (such as in the absence of a proper raceway).

[0030] Now, the inventors first determined that limiting the oxygen flow rate to the flow rate defined above has a significant synergistic effect, i.e., further limiting the actual amount of gas flowing through the channel of the soft melting zone. Therefore, the present invention aims to significantly reduce the flow rate of oxygen not only compared to a conventionally operated smelting furnace, but also compared to a smelting furnace that has been integrated to a certain extent with the use of gaseous reducing agents for operation. Secondly, the inventors unexpectedly found that due to the effect of the injected very hot first reducing gas, the cyclone can also be formed at least in part by the direct gasification of coke, as will be described in more detail below. Thirdly, it has been observed that in the absence of or almost no oxygen injection at the level of the tuyere (and therefore no or almost no coke combustion in front of the tuyere), a cyclone that allows a proper gas distribution in the furnace bosh can also be obtained mechanically at least in part by a sufficiently high injection gas velocity (such as above 150m / s, preferably above 170m / s and more preferably above 200m / s).

[0031] More importantly, however, the inventors have determined that the above-mentioned combined effects (i.e., the mechanical action and the direct coke gasification action of the injected first reducing gas) may not be sufficient to "blow out" a satisfactory gap in front of the tuyere, and the injection of a relatively small amount of oxygen, compared to the flow rate commonly used in traditional hot blast-operated blast furnaces, can ensure that the gas distribution in the furnace is appropriate and continuous. Therefore, in the method of the present invention, the amount of oxygen required for "raceway formation", "raceway maintenance" or "raceway support" is injected at the level of the tuyere, that is, the amount of oxygen sufficient to form or maintain the size and shape of the zone by burning an appropriate amount of coke in the raceway behind the injection point of the first reducing gas, or the amount of oxygen sufficient to support or supplement the mechanical effect and gasification effect described above. The injection of oxygen can be continuous or intermittent, or even controlled separately according to the actual needs for the size and shape of the raceway. In some embodiments, the flame temperature can be adjusted to a temperature between 1700°C and 2600°C, preferably between 1800°C and 2400°C, and more preferably between 1800°C and 2300°C.

[0032] Advantageously, the temperature of the injected oxygen is below 600° C. and preferably below about 400° C., such as below about 300° C., below about 200° C., or even about ambient temperature. The oxygen is preferably injected in a concentrated form, such as an oxygen content of at least about 75% by volume, more preferably at least about 90% by volume, or at least about 95% by volume, such as technical pure oxygen.

[0033] Advantageously, the density of the first reducing gas is less than about 0.80 kg / Nm 3 , preferably less than about 0.70 kg / Nm 3 , more preferably less than about 0.60 kg / Nm 3 (such as less than about 0.50 kg / Nm3 , less than about 0.45kg / Nm 3 , less than about 0.35kg / Nm 3 ) and most preferably less than about 0.30 kg / Nm 3 . In fact, the inventors envisage that another way to reduce the actual mass flow through the soft melting zone and thus achieve a proper distribution of the gases in the furnace is to use a gas with a lower density as the first reducing gas. In fact, the density of the first reducing gas can be actively controlled by reducing the content of denser substances (such as carbon dioxide, nitrogen, water, etc.) in the first reducing gas and / or by increasing the content of less dense substances in the first reducing gas (such as, in particular, by increasing the hydrogen content in the first reducing gas or by introducing helium into the first reducing gas). Another way to "overcome" the permeability problem in the soft melting zone can thus also largely prevent the phenomenon of suspended material in the upper furnace charge and significantly reduce the risk of overflow in the dripping zone. In addition, the injection of the second reducing gas above the soft melting zone will push the rising first reducing gas towards the center of the smelting furnace (such as Figure 3 In addition, injecting the first reducing gas at a temperature above 1600°C can provide most of the heat energy required to heat and melt the charge.

[0034] The introduction of a less dense substance (such as hydrogen, helium or a mixture thereof) can reduce the actual mass flow of the (first) reducing gas and can also provide the required thermal energy. In fact, as shown in the table below, the specific heat capacity of helium and especially hydrogen (here about the temperature of interest: about 1527°C) is significantly greater than that of other gases (such as CO or N 2 ) which means that to reduce the temperature by one unit, a much higher amount of heat is released per unit mass of hydrogen or helium.

[0035] Table: Specific heat capacity of different gases

[0036] CO H2 N2 He Cp at 1800K (kJ / kg.K) 1.28 16.76 1.27 10.39

[0037] However, between helium and hydrogen, hydrogen is particularly preferred because, in addition to its role as an efficient heat carrier, it also has a reduction potential that is directly useful in the blast furnace.

[0038] Having said that, the simultaneous injection of a second reducing gas at the level of the lower shaft (and its appropriate control) thereby also makes it possible to at least maintain or preferably increase the production of hot metal compared to a more conventionally operated blast furnace. Alternatively or additionally, the injection of a second reducing gas at the level of the lower shaft (and its appropriate control) makes it possible to reduce the lump coke ratio to values ​​below 160 kg / t hot metal.

[0039] In some embodiments, the density of the second reducing gas may be slightly higher than that of the first reducing gas. However, preferably, the density of the second reducing gas is less than 1.2 kg / Nm 3 , preferably less than 1.0kg / Nm 3 , more preferably less than 0.9kg / Nm 3 .

[0040] In some embodiments, the first reducing gas may be injected at a pressure between 2 and 10 bar absolute, preferably between 4 and 5 bar absolute, or even between 5 and 6 bar absolute. According to the same or other embodiments, the second reducing gas may be injected at a pressure between 2 and 10 bar absolute, preferably between 4 and 5 bar absolute.

[0041] In the context of the present invention, it is apparent that a "blast furnace" operated in accordance with the present invention is not actually a "blast" furnace per se, since the present invention substantially replaces the blast with the first reducing gas as defined herein. However, for convenience, the expression "blast furnace" as used herein may refer to a furnace operated with a blast containing air / oxygen in the context of a conventional (operating) shaft reduction and melting furnace (smelting furnace), or to a shaft reduction and melting furnace operated as described herein, wherein the blast is substantially replaced with a reducing gas (referred to herein as the first reducing gas).

[0042] In general, the first reducing gas is injected at a flow rate of less than about 800 kg / t HM, preferably less than about 775 kg / t HM, less than about 750 kg / t HM, less than about 700 kg / t HM, less than about 650 kg / t HM, and most preferably less than about 600 kg / t HM at the tuyere level. For lower lump coke ratios, the injection mass flow rate at the tuyere is generally lower. However, since a minimum flow rate of the first reducing gas must be ensured, the first reducing gas may be injected preferably at a mass flow rate of more than 60 kg / t HM, preferably more than 120 kg / t HM, more than 180 kg / t HM, or even more than 300 kg / t HM. In some embodiments, the first reducing gas may be injected at a mass flow rate of 500 Nm 3 / t HM and 1300Nm 3 / t HM, preferably 900Nm 3 / t HM and 1300Nm 3 / tHM, more preferably 770Nm 3 / t HM and 1000Nm 3 The first reducing gas is injected at a volume flow rate between / t HM.

[0043] The second reducing gas may be injected at a mass flow rate of more than 20 kg / t HM, preferably more than 50 kg / t HM, but preferably less than 600 kg / t HM, preferably less than 400 kg / t HM or even less than 360 kg / t HM. Additionally or alternatively, the second reducing gas may be injected at a mass flow rate of 200 Nm 3 / t HM and 800Nm 3 / t between HM, preferably 250Nm 3 / t HM and 700Nm 3 / t HM, more preferably 250Nm 3 / t HM and 600Nm 3 The second reducing gas is injected at a volume flow rate between / t HM.

[0044] The first reducing gas and / or the second reducing gas that can be used in the process of the present invention generally comprises synthesis gas. Although such synthesis gas can be obtained by any suitable method or source, the process of the present invention preferably comprises the further step of producing such synthesis gas by a reforming step, in particular by reforming coke oven gas, natural gas and / or other (lower) hydrocarbons or mixtures thereof, in particular by utilizing CO 2 and / or H 2 O reforming of coke oven gas, natural gas and / or other (lower) hydrocarbons or mixtures thereof. Preferably, the supply of these components may be produced by reforming the top gas of a smelter (owned or not), basic oxygen furnace (BOF) gas, open bath furnace (OBF) gas or other waste gases and process gases from a steel plant. Other suitable processes include subjecting the smelter top gas and / or coke oven gas and / or BOF gas and / or OBF gas to monoethanolamine (MEA) absorption, membrane separation, pressure swing adsorption (PSA) or vacuum pressure swing adsorption (VPSA). The reforming may be carried out by any suitable catalytic or non-catalytic reforming process or a combination of a plurality of such processes, such as steam reforming, dry reforming, etc., depending on the starting material. Advantageously, the top gas of the smelter is used as CO in the hydrocarbon reforming. 2 and / or H 2 O source, and can therefore be recycled for the preparation of the first reducing gas and / or the second reducing gas. Additionally or alternatively, the reducing gas can also be produced from a hydrocarbon source using autogenous reforming or partial oxidation technology.

[0045] According to a preferred embodiment of the present invention, the first reducing gas contains hydrogen. In fact, the inventors have found that in order to alleviate the problem of reduced voids when reducing the coke ratio, especially the permeability problem in the soft melting zone, and at the same time reduce the overflow phenomenon occurring in the dripping zone below and the influence of the suspension phenomenon occurring in the charge above, the amount of denser substances can be reduced and / or the amount of less dense substances can be increased. Although as mentioned above, it is clearly foreseen in the context of the present invention that the density of the first reducing gas is affected by the use of, for example, hydrogen, helium or both. It is very desirable to use a reducing gas with a certain proportion of hydrogen, because the density and (dynamic) viscosity of this gas are lower than the density and (dynamic) viscosity of any other gas, and it can also be used as a reducing agent. In fact, the inventors envision that the pressure drop of the entire smelting furnace / blast furnace, especially the soft melting zone and the dripping zone, is reduced to the desired level by reducing the density of the first reducing gas. The increase in the proportion of hydrogen further reduces the (dynamic) viscosity of the reducing gas, which is also conducive to better flow and distribution of the first reducing gas, especially better flow and distribution when flowing through both the soft melting zone and the dripping zone. Therefore, advantageously, the first reducing gas can be a hydrogen-rich gas, such as a hydrogen-rich synthesis gas or a gas produced by ammonia cracking and / or methanol cracking and / or ethanol cracking. The first reducing gas can have a hydrogen content higher than about 30% by volume, preferably higher than about 35% by volume, higher than about 40% by volume, higher than about 50% by volume. Values ​​higher than about 60% by volume, higher than about 65% by volume, higher than about 70% by volume, higher than about 75% by volume, higher than about 80% by volume, higher than about 85% by volume, higher than about 90% by volume, higher than about 95% by volume, and even higher than about 98% by volume are also possible.

[0046] Thus, the first reducing gas may be any suitable reducing gas having the density given above. In particular, the first reducing gas may comprise or consist of synthesis gas, such as obtained by known reforming processes. It is particularly preferred that the first reducing gas has a molar ratio (H ) higher than about 7, preferably higher than about 8 and more preferably higher than about 9. 2 +CO) / (H 2 O+CO 2 ). The molar ratio may be even higher, such as higher than about 12 or even higher than about 15. Alternatively or additionally, the first reducing gas may include ammonia cracked (N 2 +3H 2 ) and / or the cracking of methanol and / or the cracking of ethanol or the gases produced by these gases. In any case, if necessary or desired, these reducing gases can be enriched with hydrogen as described above.

[0047] It is particularly preferred that the first reducing gas is used to provide the energy required for heating, melting and proper conduct of the iron oxide reduction, or at least a significant portion of the energy. Of course, the required heating depends on the initial temperature of the first reducing gas before it is actually heated to the required temperature. Depending on the previous steps, such as the type of reforming, the first reducing gas generally has an initial temperature of 800°C to 1500°C, such as 900°C to 1300°C. Since it is preferred to inject the first reducing gas at a temperature of about 1600°C to about 2600°C, more preferably at a temperature above about 1800°C or about 1900°C and most preferably at a temperature above about 2000°C (such as above about 2150°C, about 2300°C, about 2425°C or even above about 2500°C), residual heating is provided by one or more suitable heaters, as further described below. In a particularly advantageous embodiment of the method of the invention, the actual temperature of the first reducing gas is controlled based on a plurality of operating parameters of the smelting furnace facility (such as temperature, pressure, mass / volume flow and composition of the top gas), specific charging parameters of the smelting furnace (such as temperature and flow of coke, iron oxide-containing material and / or flux), measured values ​​indicative of current operating conditions at different locations within the smelting furnace (such as temperature, pressure, composition and temperature of the products, and of course production rate, etc.). In particular, the temperature of the first reducing gas (and vice versa) can also be controlled depending on the temperature of the second reducing gas, as will be further described below.

[0048] In some embodiments, the smelting furnace facility may further include at least one sensor adapted to analyze the components of the gas at the top of the smelting furnace, including CO, CO 2 and / or H 2 concentration, and optionally also suitable for analyzing the composition of the gas, including H 2 O、N 2 and / or CH 4 The sensor may be located inside the furnace at the roof level or may be connected to a pipe recovering gas from the roof level of the furnace.

[0049] The sensor may be any type of sensor suitable for determining the gas composition, such as electrochemical, catalytic bead (thermistor), photoionization, infrared spot, infrared imaging, semiconductor or ultrasonic type sensors. The semiconductor type sensor may be a metal oxide semiconductor sensor. The sensor may be included in a gas chromatograph.

[0050] In order to impart the required energy and thus the required temperature to the first reducing gas, any known method or combination of known methods may be used, which may depend on the initial temperature of the reducing gas. Preferably, the first reducing gas is heated by one or more electric heaters before it is injected into the smelting furnace. Since the envisaged temperatures are quite high, it may be useful or desirable to apply additional heat as late as possible before the actual injection occurs, especially when the temperature is to reach above about 1800°C, such as by providing at least partial heating downstream of the furnace belly duct (for example in one or more tuyere branches, such as after the lower pipe, preferably in one or more blowpipes or even in the tuyere itself), most preferably by providing at least partial heating in one or more blowpipes or in one or more tuyere One or more plasma torches located at any suitable position. Nevertheless, it is also possible to arrange (additional) heaters (such as resistance or plasma electric heaters) upstream of one or more tuyere branches, for example in the furnace belly duct or even upstream of the furnace belly duct (downstream of the reformer), and is therefore explicitly considered in the context of the present invention. In a preferred embodiment, the first reducing gas can be heated by electric heaters (i.e., electrically driven heaters), each of which is suitable for operating at an electric power of 200kWh / t HM to 700kWh / t HM, 250kWh / t HM to 600kWh / t HM or 300kWh / t HM to 550kWh / t HM.

[0051] In the case where the first reducing gas is heated (at least partially) by one or more plasma torches arranged in the blowpipe of, for example, one or more tuyere branches, the plasma torch is preferably an electrode-based plasma torch or an electrodeless plasma torch selected from a plasma torch such as one ignited by induction, a microwave plasma torch, a radio frequency plasma torch, and a combination thereof. Suitable plasma torches are DC plasma torches or AC plasma torches, such as three-phase AC plasma torches, wherein the plasma torches generally have a rated electrical power of 1 MW to 10 MW, preferably 2 MW to 6 MW, and most preferably 4 MW to 5 MW. More details on suitable plasma torches and appropriate locations within the smelting furnace facility will be provided below.

[0052] In contrast to the first reducing gas, the second reducing gas is not usually injected at such a high temperature, but similar temperatures may be used if deemed necessary or desirable. In fact, in most cases, it is preferred to inject the second reducing gas at a temperature of about 800°C to about 1200°C, more preferably at a temperature of about 900°C to about 1100°C, and most preferably at a temperature below about 1000°C (such as, below about 950°C). As already briefly mentioned in the context of the temperature of the first reducing gas, the actual temperature of the second reducing gas is preferably controlled based on one or more of a plurality of operating parameters of the smelting furnace facility (such as coke reactivity temperature, pressure, mass / volume flow rate and composition of the top gas), specific charging parameters of the smelting furnace (such as the temperature and flow rate of coke, iron oxide-containing material and / or flux), and measured values ​​indicating current operating conditions at different locations within the smelting furnace (such as temperature, pressure, gas composition, etc.). In particular, the temperature of the second reducing gas (etc.) may also be controlled based on the temperature of the first reducing gas, and vice versa.

[0053] The smelting furnace facility may further comprise a gas injector regulating device configured to adjust the gas composition and / or gas volume injected by the first injector device and / or the second injector device based on the determined gas composition and / or temperature at the furnace top.

[0054] The gas injector regulating device may also adjust the power supplied to the at least one electric heater based on the determined gas composition at furnace roof level and / or the temperature at furnace roof level.

[0055] The gas injector adjustment device may also be configured to adjust the composition of the gas injected by the first injector device and / or the volume of the injected gas and / or the temperature of the gas based on the composition and / or temperature of the hot metal output by the smelting furnace and the hot metal production rate. In order to determine the composition of the hot metal output by the smelting furnace and the hot metal production rate, the smelting furnace facility may include other sensors located at the hot metal outlet of the furnace configured to determine the composition of the hot metal and determine the volume of the hot metal.

[0056] In the present invention, the lump coke supplied to the smelting furnace is relatively low compared to a conventionally operated blast furnace. However, in particular in the soft melting zone, the permeability is also significantly reduced due to the penetration of the molten slag into the coke layer and blocking part of its height. Since this will reduce the permeable height of the coke layer, it is generally not recommended to supply coke in a layer without a minimum height. This minimum height is generally at least about 8 cm (such as at least about 10 cm, such as between 9 cm and 11 cm), at least about 12 cm or at least about 15 cm (such as 14 cm to 15 cm).

[0057] In some further embodiments, the method disclosed herein further specifically includes the following steps: controlling the amount (injection rate) and / or component of the second reducing gas injected at the furnace body level according to the amount (injection rate) and / or component of the first reducing gas injected at the tuyere level and / or the amount (injection rate) of oxygen (if any) injected at the tuyere level, thereby adjusting the average reduction degree of the iron-oxide-containing material reaching the soft melting zone to a value higher than about 80%, more preferably higher than about 85%.

[0058] As already mentioned, the desired lump coke ratio depends on, among other things, the amount of coke consumed by direct reduction of the iron ore. In some embodiments, the lump coke ratio can thus be reduced by controlling the lump coke consumed by direct reduction, which in turn can be controlled by adjusting the amount (injection rate) and / or composition of the second reducing gas injected at the furnace shaft level according to the amount (injection rate) and / or composition of the first reducing gas injected at the tuyere level and / or the amount (injection rate) of oxygen (if any) injected at the tuyere level. Thus, by controlling the coke consumed by direct reduction to below about 60 kg / t HM, preferably below about 50 kg / t HM, more preferably below about 40 kg / t HM, the lump coke ratio can be (further) reduced to a value such as below 220 kg / t HM.

[0059] Alternatively or additionally, the method of the present invention preferably further comprises the step of reducing / limiting the channeling effect / phenomenon above the soft melting zone by controlling the injection (flow rate, velocity and pressure) of the second reducing gas in the (lower part of) the shaft of the smelting furnace. This advantageous effect is achieved due to the following reasons: the second reducing gas is injected at the level of the shaft, preferably along the periphery of the smelting furnace, so that the gas rising from the soft melting zone is centered in the smelting furnace. Therefore, it is recommended that the first reducing gas injectors (i.e., tuyere) and / or the second reducing gas injectors are evenly distributed, with a distance between each other generally between 0.5m and 2.5m and preferably between 1.0m and 1.5m. In addition, the injection velocity of the second reducing gas at the level of the shaft can advantageously be controlled to a value between 40m / s and 250m / s, such as preferably between 80m / s and 200m / s. It is also generally beneficial or desirable to control the ratio between the volume flow rate of the second reducing gas (injected at the level of the furnace shaft) and the volume flow rate of the first reducing gas (injected at the level of the tuyere) to a value of 0.1:1 to 1:1, preferably 0.2:1 to 0.8:1, more preferably 0.33:1 to 0.7:1 or even 0.4:1 to 0.7:1, 0.65:1 or 0.6:1.

[0060] As already stated above, the second reducing gas that can be used in the process of the invention generally comprises synthesis gas. The second reducing gas can also consist only of synthesis gas, which means that the second reducing gas has an original composition obtained, for example, by a reforming process (preferably by the reforming process mentioned above). Regardless of the source or pretreatment of the second reducing gas, it is particularly preferred that the second reducing gas has a molar ratio (H / ) higher than about 6, preferably higher than about 7 and more preferably higher than about 8. 2 +CO) / (H 2 O+CO 2 ). The molar ratio may be even higher, such as higher than about 12 or even higher than about 15. In some embodiments, the molar ratio may be lower than about 80 or lower than about 30.

[0061] The second reducing gas may be rich in hydrogen, such as a hydrogen-rich synthesis gas. Regardless of its original composition, the second reducing gas advantageously has a (final) hydrogen content of greater than about 30% by volume, preferably greater than about 40% by volume, more preferably greater than about 50% by volume.

[0062] It is further preferred that the first reducing gas and / or the second reducing gas (preferably both) are substantially free of nitrogen (if any). Thus, the first reducing gas and the second reducing gas preferably (independently) have a nitrogen content of less than about 35% by volume, more preferably less than about 15% by volume, still more preferably less than about 10% by volume, and most preferably less than about 5% by volume.

[0063] The method of the invention preferably also comprises: actively controlling the pressure level of any gas injected at the tuyere. Advantageously, the pressure level of the smelting furnace at the tuyere level is controlled to a value higher than about 2 barg, preferably higher than about 4 barg and more preferably higher than about 5 barg. In fact, higher pressure levels also have a positive effect on the overflow phenomenon (i.e. the pressure exerted on the droplets). The higher the pressure, the greater the density and the lower the velocity of the gas. Since the effect of the gas on the droplets depends more on the velocity (the square of the velocity) than on the density, an increase in pressure will help to further improve the situation in the soft melting zone and the dripping zone.

[0064] In some advantageous embodiments, the method further comprises the step of reducing channeling and overflowing effects by controlling the top pressure of the smelting furnace within a range of 1 barg to 10 barg, more preferably within a range of 2 barg to 7 barg, and most preferably between 3 barg and 5 barg.

[0065] Alternatively or additionally, the method may further include the following steps: reducing the wall channel effect of the gas from the soft melting zone on the furnace wall in the lower furnace body area by controlling the injection conditions of the second reducing gas (such as, specifically, the injection speed and / or flow rate of the second reducing gas injected into the furnace body of the smelting furnace).

[0066] In the process of the present invention, it may be advantageous to include a further step of reducing the carbon dioxide content of any one or more carbon dioxide-containing waste gases and / or process gases produced during operation by carbon capture and utilisation (CCU) and / or carbon capture and storage (CCS).

[0067] In this context, of particular interest is the use of at least a portion of the captured CO in so-called synthesis gas production plants. 2 , for example by mixing carbon dioxide with low CO 2 The hydrogen is converted into synthesis gas and further converted into synthetic hydrocarbons (such as natural gas) by methanation, and / or by any other suitable production process (including biological processes) to produce methane, methanol, ethanol, etc. All or part of the methane, methanol, ethanol, etc. can then be used for synthesis gas production, which can be injected into the blast furnace.

[0068] As mentioned above, in the method of the present invention, within the range of acceptable nitrogen concentration of the synthesis gas, ammonia (NH 2) is also added as a hydrogen-rich fuel. 3 ) and / or cracked ammonia (N 2 +3H 2 ) may be advantageous, both being used as the first reducing gas and / or the second reducing gas. In fact, if the hydrogen content is high and there is no CO 2 It would be of particular interest if the energy carrier ammonia were to become commercially available.

[0069] The expression "at the level of the shaft" or "injected at the level of the shaft of the smelting furnace..." means that the injection is carried out in the lower shaft area above the hot blast level / tuyere level, in particular in the ferrous oxide gas-solid reduction zone above the bosh, preferably above the soft melting zone. Preferably, the injection at the level of the shaft can thus be carried out above the base of the soft melting zone (for example, in close proximity to the soft melting zone), the area of ​​the soft melting zone directly contacting the furnace wall (i.e., above the base of the soft melting zone). In other words, the equivalent expression "at the level of the shaft" or "at the lower shaft level" refers to a position allowing the injected gas to participate in the reduction reaction, preferably a position in the FeO reduction zone. In contrast, the expression "at the level of the tuyere" or "injected at the level of the tuyere of the smelting furnace..." means that the injection is carried out at a position where hot blast tuyere is conventionally provided, preferably using conventional tuyere located in the lower part of the bosh (i.e., directly below the soft melting zone).

[0070] "Injector device" in the context of the present invention is understood to include one or more injectors, optionally including any corresponding related upstream connecting ducts, pipes and regulating and control components, reducing gas treatment / heating / cooling, etc. Depending on the specific context, the first injector device located at the tuyere level may thus refer to one or more tuyere itself or one or more of said tuyere with any one or more related upstream components (such as one or more blowpipe assemblies or one or more tuyere branches, bosh branches, first reducing gas treatment or heating units, connecting pipes and control components, etc.). Similarly, the second injector device located at the shaft level may refer to one or more shaft injectors itself or one or more of said shaft injectors with any one or more related upstream components (such as one or more injector supply assemblies, shaft annular ducts, second reducing gas treatment or heating units, connecting pipes and control components, etc.), depending on the specific context.

[0071] In some embodiments, the first injector device may include at least 10 first gas injectors (i.e., tuyere) and at most 70 first gas injectors (i.e., tuyere), preferably, 18 to 40 first gas injectors. According to the same or other embodiments, the second injector device may include at least 10 second gas injectors and at most 70 second gas injectors, preferably, 18 to 40 second gas injectors.

[0072] The expression "equivalent coke ratio" includes all carbon-containing solid or liquid (at ambient temperature) materials fed to the smelting furnace, including actual coke material (fed in lump coke ratio), but also other carbon-containing gaseous, solid or liquid materials that can be added to the operating smelting furnace, such as gaseous methane, natural gas and / or coal powder injected at the tuyere level. If necessary or considered helpful, coal powder or other carbon-containing gaseous, solid or liquid materials can be injected at the tuyere level to provide the required energy by combustion in the furnace when the first reducing gas is injected, for example at a temperature below 1600° C. (temporarily, for example due to lack of heating means) and / or when restarting after maintenance stops. However, the injection rate of other carbon-containing materials is preferably below 150 kg / t HM, more preferably below 120 kg / t HM. However, most preferably, the method of the present invention does not supply these further gaseous, solid or liquid carbonaceous materials to the smelting furnace / blast furnace. Specifically, the method of the present invention does not consider or include the injection of pulverized coal into the smelting furnace / blast furnace, but only supplies coke as a carbonaceous solid material to the top of the smelting furnace / blast furnace. Therefore, the expression "lump coke ratio" used herein represents the flow rate of coke material actually added to the top of the blast furnace. In fact, "lump coke" refers to coke charged into the furnace, and the size is generally greater than 20mm. In some preferred embodiments, the furnace is operated with a (total) equivalent coke ratio of less than 220kg / t HM, preferably less than 200kg / t HM and more preferably less than 180kg / t HM.

[0073] Flow rates expressed as “ / t HM” refer to tonnes (metric tons) of hot metal produced by the blast furnace facility. 3 ” refers to normal cubic meter and means 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 atmosphere (101.325 kPa).

[0074] In the context of the present invention, the expression "hydrogen-rich" or "enriched with hydrogen" with respect to a gas (mixture) means that hydrogen (H 2 ) is added to the gas (mixture) to increase the molar proportion of hydrogen in the resulting hydrogen-rich gas (mixture).

[0075] In the context of the present invention, the oxygen injection rate at the tuyere level refers to the total amount of oxygen injected.

[0076] In the context of the present invention, "reducing gas" refers to a gas that is capable of participating in (i.e., performing) a reduction reaction, i.e., a gas containing reducing substances (such as H 2 and / or CO) gas, preferably, in the reducing gas, H 2 30% to 100% by volume, CO occupies 10% to 70% by volume, and in addition to CO and H2 Compounds other than 25% by volume may account for less than 35% by volume, more preferably less than 10% by volume or even less than 5% by volume. In some embodiments, the reducing gas has a hydrocarbon concentration lower than 25% by volume, preferably lower than 20% by volume and more preferably lower than 10% by volume.

[0077] In the context of the present invention, “about” means that a given numerical value covers a value range of -10% to +10% of said numerical value, preferably covers a value range of -5% to +5% of said numerical value or even covers a value range of -2.5% to +2.5% of said numerical value.

[0078] The method of the present invention and other variations disclosed herein have a number of important advantages and benefits:

[0079] -CO 2 Lower emissions,

[0080] - The method can be implemented on existing blast furnaces with only limited modifications, without changing the layout and logistics of the steel plant,

[0081] - Due to the furnace shaft injection, the tuyere gas volume can be reduced by about 15% to 30%, thereby reducing the lump coke layer thickness by about 25% to 50%,

[0082] - there is little or no coke combustion in the smelting furnace, and therefore little or no oxygen demand,

[0083] -Since the first reducing gas contains H 2 , the dynamic viscosity of the gas can be reduced by about 15%, allowing higher velocities at the same pressure drop and with the same forces on the coke particles and droplets,

[0084] -Since the first reducing gas contains H 2 , the density of the gas can be reduced by about 50%, allowing higher velocities at the same pressure drop and with the same forces on the coke particles and droplets,

[0085] - Very low coke consumption is usually achieved without the need for pulverized coal or auxiliary fuel injection, and

[0086] - Since the syngas is produced outside the furnace by processes such as steam reforming or by injection of H 2 generated, so it is easy to restart. BRIEF DESCRIPTION OF THE DRAWINGS

[0087] Preferred embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which:

[0088] Figure 1 is a schematic diagram of an advantageous embodiment of the present invention.

[0089] Figure 2 is a schematic partial cross-sectional view of an advantageous embodiment of (a part of) a first injector device for use in the present invention.

[0090] Figure 3 The individual zones within the blast furnace and the effect of the reducing gas B injected in the lower shaft on the rising gases flowing through the coke layer in the remelting zone are shown.

[0091] Other details and advantages of the present invention will become apparent from the following detailed description. DETAILED DESCRIPTION

[0092] General considerations

[0093] Blast furnace in CO 2 The main problem in terms of emissions is that the blast furnace process is based on the reduction of iron ore with coke and also on the injection of a carbon-rich auxiliary fuel / reducing agent at tuyere level.

[0094] It has been proposed to inject syngas in the furnace shaft or even at tuyere level to help reduce coke consumption in the blast furnace and thereby reduce CO 2 Even under these conditions, however, a non-negligible lump coke ratio is still required, which is usually still above 300 kg / t HM. This need for a still considerable coke ratio is mainly determined by the process and to a lesser extent by mechanical / fluid dynamic reasons.

[0095] Nowadays, blast furnaces seem to be increasingly replaced by alternative process routes that require only small amounts of coke. In fact, these processes divide the blast furnace into two sections: the iron ore reduction section, which takes place in a shaft furnace, and the melting section, which takes place in an electric furnace, using arc / plasma or immersed electrodes. However, this concept leads to very large and complex facilities, which are very costly in terms of capital expenditure and are also difficult to maintain. Moreover, in the case of direct reduced iron (DRI) with hydrogen reduction, the furnace still requires a considerable amount of coke, of the order of 60 kg / t HM to 110 kg / t HM. This carbon is needed to complete the reduction of the DRI and to carburize the hot metal, which is then treated in a basic oxygen furnace.

[0096] The method of the present invention is intended to be able to demonstrate that widely used blast furnace technology, if properly converted as described herein, can provide CO 2 Lower emission solutions, enabling the use of (modified) blast furnaces with very low coke ratios by improving the process conditions in the blast furnace.

[0097] In fact, today's conventional blast furnaces use coke to meet different needs:

[0098] - Indirect reduction of iron ore in the furnace shaft:

[0099] 3Fe 2 O 3 +CO→2Fe 3 O 4 +CO 2 and Fe 3 O 4 +CO→3FeO+CO 2

[0100] - Direct reduction of iron oxide is carried out in the lower part of the blast furnace, directly reducing molten iron oxide as follows:

[0101] FeO+C→Fe+CO

[0102] -Dissolution loss: At a certain temperature level, coke reacts with carbon dioxide and H 2 O reacts to form carbon monoxide and H 2 :

[0103]

[0104] -Carburization of molten iron. At the typical operating temperature of a blast furnace (approximately 1500°C), iron saturated with carbon contains about 4.5% dissolved carbon. This is also a prerequisite for a blast furnace, as it allows the hot metal to be liquid at this temperature level.

[0105] -The coke is burned at the tuyere to produce the hot reducing gases required to melt and reduce the iron ore. The hot reducing gases should reach the minimum flame temperature required for the operation of the blast furnace (1800°C to 2600°C). In fact, this flame temperature ensures the heat transfer from the gas phase to the ore and its subsequent melting. If this temperature is too low, the blast furnace will not achieve high production.

[0106] -Due to chemical equilibrium, about half of the reducing gas produced in the blast furnace leaves the furnace top without reacting (top gas). Usually 1 / 3 of the remaining calorific value of the top gas is used to heat the hot blast, and 2 / 3 is discharged from the blast furnace plant.

[0107] In today's standard blast furnace application, the coke rate is 310 kg / t HM and the pulverized coal injection (PCI) is 180 kg / t HM. The coke consumption distribution for different factors is as follows, see Table 1.

[0108] Table 1

[0109]

[0110] Now the question is how to reduce the coke ratio?

[0111] Coke dissolved in the hot metal cannot be reduced practically, since the coke will dissolve in the hot metal until it is saturated. Saturating the hot metal with carbon also ensures a long life of the carbon blocks in the furnace. Therefore, in principle this 47 kg / t HM (see Table 1) cannot be reduced.

[0112] If the degree of reduction of the ore from the upper part of the blast furnace is increased, the coke required for direct reduction in the lower part of the blast furnace may be significantly reduced. This can be achieved by increasing the ratio of reducing agent to oxidizing agent (CO + H 2 ) / (CO 2 +H 2 O) to increase the degree of reduction. This can be achieved by increasing the reducing gas flow, for example by injecting reducing gas at the bottom of the furnace. Another option is to increase the H in the injected gas at the tuyere level and at the furnace level. 2 +CO accumulation (mainly by reducing N 2 content) to achieve.

[0113] The coke loss required can also be reduced by increasing the ratio of reducing agent to oxidizing agent in the gas flowing through the blast furnace shaft. This can be achieved by increasing the reducing gas flow rate, for example by injecting reducing gas at the bottom of the shaft. Similarly, the H content of the injected gas at the tuyere level and the shaft level can be increased. 2 +CO accumulation (such as by reducing N 2 content) to achieve.

[0114] The energy required for the lower part of the blast furnace is generated at the tuyere level, where coke and auxiliary fuel (such as PCI or natural gas) are burned and gasified with hot blast (between 900° C. and 1300° C.), and tuyere gases with a temperature between 1800° C. and 2500° C. are produced. For this purpose, a large amount of fuel is burned, since the fuel is only oxidized to CO and not to CO. 2 . Complete combustion occurs in an oxidizing atmosphere to form CO 2 and H 2 This results in a much lower release of reaction heat and therefore a much lower flame temperature than in the case of O.

[0115] The objects of the present invention are:

[0116] In the present invention, it is proposed to combine two types of injection, i.e., to inject reducing gas in the blast furnace both at the bottom of the shaft and at the tuyere level, wherein the reducing gas injected at the tuyere level is further heated to a temperature similar to or as close as possible to the conventional blast furnace flame temperature, while significantly reducing the injection of oxygen. Thus, the present invention contemplates heating the tuyere reducing gas (e.g., synthesis gas) to at least 1600°C, preferably above 1800°C, more preferably above 2000°C and possibly even above 2300°C.

[0117] When the hot reducing gas is injected at the level of the furnace body and the tuyere, the method of the invention completely avoids the a priori requirement for oxygen-containing hot air. However, according to the invention, if necessary or considered helpful, it is recommended to provide a small amount (such as less than 120 Nm ) at the tuyere with or without some auxiliary fuel (such as natural gas, coke oven gas, coal powder, etc.). 3 / t HM, preferably less than 112Nm 3 / t HM) of cold oxygen injection. Usually, the minimum injection rate of oxygen at the tuyere level is higher than about 4Nm 3 / tHM, such as above about 12Nm 3 / t HM, higher than about 25Nm 3 / t HM, for example, higher than about 35Nm 3 / t HM or even above about 50Nm 3 / t HM.

[0118] For heating the (first) reducing gas, different methods can be used to effectively heat the reducing gas, for example from the synthesis gas production temperature (about 950° C. in the case of catalytic reforming processes and partial oxidation / autothermal reforming, about 1200° C. in the case of non-catalytic reforming processes, preheating temperature or non-preheating temperature (0 to 1300° C.) in the case of (V)PSA) to the desired / required temperature. Technologies that can be used for this purpose are known. Advantageously, electrical energy can be used for this purpose, in particular "green" or renewable electrical energy, for example by resistive heating and / or plasma technology.

[0119] Furthermore, the reducing gas may be produced by any suitable method, such as in CO 2 Reducing gases are produced in removal plants (e.g., amine-type adsorbers, PSA or VPSA) starting from blast furnace gas, basic oxygen furnace gas or other gases, where CO can be increased by using an adsorption-enhanced water gas shift reactor. 2 The reducing gas may also be a hydrogen-rich stream from a hydrogen removal unit.

[0120] Furthermore, the use of pure hydrogen as reducing gas, or the use of N produced by the cracking of ammonia as mentioned above (or even the cracking of methanol and / or ethanol), is also expressly foreseen. 2 and H 2 mixture.

[0121] In the process disclosed herein, by almost completely eliminating nitrogen from the gas flowing through the blast furnace and injecting the gas into the blast furnace at approximately the flame temperature, it is in principle possible to achieve a coke ratio of about 100 kg / t HM.

[0122] As an alternative to heating the synthesis gas injected at the tuyere, it is also possible to supply electricity directly to the blast furnace, for example by using plasma torches directly immersed in the blast furnace, electrodes, by induction heating and the like.

[0123] In reformer, PSA, VPSA, CO 2 It is particularly advantageous to reprocess part of the blast furnace top gas in a removal plant etc. to produce reducing gas with an appropriate ratio of reducing agent to oxidizing agent. The method of the invention contemplates various processes for producing reducing gas and injecting the reducing gas together with hydrogen and / or cracked ammonia into the blast furnace at shaft level and tuyere level.

[0124] It is also considered to use part of the blast furnace top gas as heating fuel for synthesis gas production. Only a small part of the blast furnace top gas can leave the blast furnace plant, which shows a high efficiency.

[0125] Due to the permeability, the coke ratio may not be able to reach below 90 kg / t HM, but the process of the present invention enables the coke ratio to be significantly lower than 200 kg / t HM.

[0126] As explained above, the permeability problem is the main reason why part of the reducing gas is not injected at the level of the tuyere but at the bottom of the furnace body. In fact, reducing the coke ratio to the minimum level reduces the passage area of ​​the rising gas in the soft melting zone. This increases the gas velocity and pressure drop in the soft melting zone and the upper dripping zone, and may also lead to abnormal distribution of the gas in the radial and circumferential directions. Therefore, it is very important to reduce the gas volume in the tuyere and furnace belly area, which can be achieved by partially injecting the reducing gas at the level of the furnace body. It is also advantageous to reduce the density and viscosity of the reducing gas. This can be achieved by using a hydrogen-rich reducing gas, which is additionally rich in hydrogen or is not rich in hydrogen and has a very low density and viscosity, which in turn reduces the pressure drop and reduces the gas velocity.

[0127] The process of the present invention still requires the use of some coke and may require, for example, methane to reform the recovered top gas. 2Additional CO can be achieved when methanating gases (such as blast furnace top gas and / or basic oxygen furnace gas) to produce natural gas. 2 Emission reduction. As a substitute for natural gas, methane produced through methanation can also be used to further reduce CO 2 Emissions.

[0128] Finally, the method of the present invention may also include capturing CO from the exhaust gas of the reformer / heater or any other process gas of the steel plant. 2 for use or storage, thereby further reducing CO 2 total emissions.

[0129] Case Study: Reducing Gas Utilization in Blast Furnaces

[0130] In order to better illustrate the present invention, several cases were studied in more depth. The details of these cases are given in Table 2 below.

[0131] Case 1 and Case 2 are currently operating blast furnaces, in which the crude coke ratios are 255 kg / t HM and 205 kg / t HM, respectively.

[0132] Case 3 and Case 4 are respectively for injecting hot H 2 A blast furnace that does not inject hot hydrogen into the furnace body and a blast furnace that injects hot hydrogen into the tuyere and the furnace body.

[0133] Cases 5 and 6 concern new furnaces with lump coke ratios of about 180 kg / t HM and about 100 kg / t HM, in which superheated synthesis gas is injected at tuyere level and a small amount of oxygen is injected at tuyere level as required.

[0134] Cases 7 and 8 concern new furnaces with lump coke ratios of about 180 kg / t HM and about 100 kg / t HM, in which superheated synthesis gas is injected at tuyere level and, in addition, hot synthesis gas is injected into the furnace shaft and, if required, a small amount of oxygen is injected at tuyere level.

[0135] Case 1 represents a typical well-run blast furnace with high pulverized coal injection (PCI), several of which can be found around the world, especially in Europe. PCI can reduce the lump coke rate or raw coke rate to a value of about 250 kg / t HM.

[0136] As can be seen, the furnace requires about 235 Nm per tonne of hot metal (t HM) produced. 3 of oxygen. Some of the oxygen comes from heated air, while the other part comes from enriched oxygen, the pure oxygen in which comes from an air separation plant.

[0137] This oxygen enrichment is necessary because the blast furnace requires a certain flame temperature to function properly. In fact, this flame temperature ensures that the reduced ore can be melted and that the injected coal can burn in the raceway. In the case of high PCI, the required flame temperature is about 2200 ° C.

[0138] In this case, it is not possible to dispense entirely with the natural blast, since a certain volume of gas is required to have sufficient latent heat to supply the energy required to heat and reduce the ore in the shaft of the furnace.

[0139] Case 2 represents a typical blast furnace with abnormally high PCI injection. Such operation has been going on for a long production period of several months. However, the operation is quite challenging and requires high operating skills and very high-quality raw materials, especially high-cost premium coke. In this case, it is worth noting that the coarse coke ratio has reached 205kg / t HM.

[0140] If the injection conditions at the tuyere are compared, it can be seen that the oxygen enrichment must be further increased, but in general, the conditions at the tuyere, the hot blast temperature, the gas volume flow rate, have not changed much.

[0141] If you want to reduce CO in hot metal production 2 Emissions, both operations are of course not ideal since the entire energy and reductant inputs are coal based.

[0142] Case 3 and Case 4: In these cases, the inventors analyzed the operation of blast furnaces that used higher hydrogen injection rates to reduce part of the energy and reducing agent input from coal and utilized CO2-free 2 of hydrogen instead.

[0143] It is well known that when cold hydrogen and oxygen-enriched hot air are injected at the tuyere at the same time, a large amount of hydrogen cannot be injected. The typical maximum hydrogen utilization is limited to less than 30kg / t HM.

[0144] Therefore, the method of adding hydrogen needs to be changed. Hydrogen needs to be injected in high temperature form, injected only at the tuyere level, or injected at both the tuyere level and the furnace level.

[0145] Regarding the injection temperature, the inventors assumed an injection temperature of 950° C. at the furnace level and an injection temperature of 1200° C. at the tuyere level. These temperatures are generally achievable when using conventional heat exchangers and regenerative heaters.

[0146] At the tuyere level, cold oxygen now needs to be added to burn some of the coke to reach the flame temperature required to melt the ore. It is known from furnaces not using PCI injection that in this case the flame temperature can be reduced to a minimum of about 1800°C, always requiring sufficient flow to supply enough energy to melt the reduced ore and to supply energy for heating and reducing the ore in the shaft of the blast furnace.

[0147] As can be seen, the oxygen injection at the tuyere can be increased from about 240 Nm 3 / t HM is reduced to 150Nm 3 / tHM and 180Nm 3 / t HM. Therefore, less carbon needs to be burned at the tuyere. However, since there is no available carbon for PCI injection, the coke that needs to be burned at the tuyere is as high as in Case 1 and Case 2, resulting in an increase in the coke ratio.

[0148] When using hydrogen in a blast furnace additional coal / coke is required and therefore CO reduction is required 2 This contradiction in emissions cannot be overcome by conventional methods.

[0149] In addition, it can be seen that in both cases with and without shaft injection, pure H 2 The injection requires a large amount of hydrogen. In the case of furnace body injection and without furnace body injection, the hydrogen required per ton of hot metal is 1070Nm 3 and 1280Nm 3 This far exceeds the hydrogen requirements of other production routes, such as the need for about 660Nm 3 / t HM hydrogen direct reduction process. In addition, the required coke ratio in these cases is quite high, making them unattractive.

[0150] In order to overcome this problem, the inventors proposed to inject synthesis gas with or without pure hydrogen into the blast furnace at superheated temperature, and at the same time inject a small amount of oxygen at the tuyere level as needed.

[0151] Superheating can be achieved, for example, by means of a plasma torch.

[0152] Case 5 and Case 6: In both cases, superheating the gases injected at the tuyere has the advantage that little or no combustion of the coke with oxygen is now required to obtain the tuyere temperature level required for smelting and reducing the ore.

[0153] Case 7 and Case 8: These cases inject additional synthesis gas into the furnace shaft compared to Case 5 and Case 6. Again, superheating the gas injected at the tuyere has the advantage that now little or no combustion of coke with oxygen is required to obtain the tuyere temperature level required for melting the reduced ore. However, since the inventors propose to operate the furnace by partially injecting the gas into the furnace shaft, they are able to supply the temperature level required for melting with a lower plasma torch power demand. In addition, with the furnace shaft injection, less gas needs to flow through the high resistance soft melting zone area.

[0154] Furthermore, Case 5 can be compared with Case 7, respectively, and Case 6 with Case 8. Although Case 5 and Case 7 and Case 6 and Case 8, respectively, are comparable in terms of the injection of oxygen, in Case 7 and Case 8, less gas needs to enter the tuyere, which is seen as allowing to work with a "smaller" raceway. In fact, as can be seen in Case 5 and Case 7 when more oxygen is used, the coke ratio is higher because more coke is burned, while in Case 6 and Case 8, almost no coke is burned because there is only little oxygen, and in both cases the main coke consumption at the tuyere comes from gasification.

[0155] In contrast to Case 7 and Case 8, in Case 5 and Case 6, all the reducing gas required for operation needs to pass through the tuyere and thereby through the dripping zone and the soft melting zone, which will cause overflow and hanging material problems, respectively. In addition, in Case 5 and Case 6, there is no way to avoid the above-mentioned wall channel phenomenon.

[0156] By operating the blast furnace as described herein, it is now practically possible to achieve the very low coke ratios given in Case 7 and Case 8, namely about 180 kg / t HM and about 100 kg / t HM respectively.

[0157] It can also be seen that at 100kg / t HM and 440Nm 3 / t HM, the amount of pure hydrogen used is also very low.

[0158] This can be achieved, for example, by recycling the top gas of the blast furnace back into the blast furnace. To this end, it is necessary to reduce the H 2 O and CO 2 The H content can be easily reduced by cooling and condensation. 2 O.CO 2 The elimination of CO is somewhat more complex and different approaches have been proposed, such as PSA, VPSA and reforming CO with hydrocarbons. 2 To form CO and H 2 .

[0159] In this example, natural gas reforming is used.

[0160] The reforming can be carried out catalytically at temperatures of about 950° C. or in a regenerative reformer type without a catalyst at high temperatures of >1100° C. The latter type is very suitable for preparing the gas at the tuyere level, since very high temperatures are required especially at the tuyere level.

[0161] In addition, when the gas is reformed at high temperature, a very high degree of gas reduction, i.e. (CO+H 2 ) / (CO 2 +H 2 O)>7, preferably>8, more preferably>9. A higher degree of reduction is very important for achieving a lower coke ratio, because each CO in the gas 2 and H 2 O will consume the coke in the raceway.

[0162] Table 2:

[0163]

[0164]

[0165] The volume flow rates of these gases are summarized in Table 3 below:

[0166]

[0167]

[0168] Coke consumption

[0169] The coke in the BF is consumed by: loss reaction in the furnace shaft, carburization, liquid direct reduction (upper part of the dripping zone) and coke gasification / combustion in the tuyere. In addition, a small amount of coke powder is emitted into the dust during charging of the furnace.

[0170] In the following Table 4 the amount of coke consumed by the mentioned means (coke redistribution) is given for all cases.

[0171]

[0172]

[0173] It can be seen that for the new furnace conditions, the coke consumption by liquid direct reduction is significantly reduced. The reason is that the reducing power (H 2+CO) is very high, and the iron charge in the furnace shaft is reduced to a very high degree. Therefore, there is less FeO left to be reduced to Fe by direct reduction and loss reaction. For Cases 5 to 8, the coke consumption by direct reduction is less than 20kg / t HM, while for the conventional furnace, the coke consumption by direct reduction is more than 70kg / t HM.

[0174] It can also be seen that the injection of reducing gas into the furnace shell limits the consumption of coke by solution loss and thus chemical attack on the coke is less in Cases 7 and 8. Therefore, it can be considered that the injection of reducing gas does not lead to an increase in the amount of coke required for the new furnace cases.

[0175] Furthermore, since the superheated reducing gases carry a large amount of heat energy into the blast furnace, the amount of coke burned in the tuyere is reduced. Nevertheless, the reducing gases contain a small amount of H 2 O or CO 2 These gases are converted into CO and H by reacting with carbon in the cyclotron region. 2 . Therefore, some coke will be consumed in this zone. This can be seen by comparing Case 7 and Case 8. By injecting very hot reducing gas, a non-negligible portion of the coke can be gasified (rather than burned), thus helping to form and maintain the cyclotron zone even at very low injected oxygen flow rates.

[0176] What has been described here shows how the coke ratio can be reduced to very low levels using superheated reducing gases injected into the tuyere and hot reducing gases injected into the furnace shaft level. Only carburization cannot be reduced by reducing gases.

[0177] The overflow and pressure drop in the soft melting zone (melting zone) are explained in detail:

[0178] The purpose of this description is to illustrate the relative rather than absolute changes in the overflow phenomenon and pressure drop in the dripping zone and the soft melting zone inlet when the blast furnace is converted from high coke rate operation to low coke rate operation:

[0179] For overflow, the following dimensionless parameters are used:

[0180] The dimensionless parameters of the Matsu-ura and Ohno diagram and the variables and units used in their calculations are shown in parameters (1) and (2) below:

[0181] Dimensionless pressure drop:

[0182]

[0183] ΔP, gas pressure drop between two points (Pa); ΔL, bed length measurement ΔP d(m); ρ l , liquid density (kg / m 3 ); g, acceleration due to gravity (m / s 2 ).

[0184] Dimensionless irrigation density:

[0185]

[0186] σ, liquid surface tension (N / m); ρ l , liquid density (kg / m 3 ), μ, liquid viscosity (Pa s); ε, void ratio (-); d p , particle harmonic diameter (m); u, apparent liquid velocity based on empty tower conditions (m / s); θ, contact angle between liquid and solid (°).

[0187] For all variables, the liquid considered is the slag. Since the viscosity of the slag is higher than that of the hot metal and the density of the slag is lower than that of the hot metal, the slag will overflow first.

[0188] In parameter (1), the first term of the dimensionless pressure drop, only the pressure drop ΔP depends on the gas properties.

[0189] Parameter (2), ie the second term of the dimensionless filling density, has no parameters that depend directly on the gas properties, but only depends on the gas properties indirectly through the coke particle void fraction and the coke particle diameter.

[0190] In fact, increasing the reducing agent (H 2 The flow rate and concentration of CO and CO) will result in a reduction in the coke consumption of the coke required for indirect reduction in the furnace shaft (via Boudouard reaction) and direct reduction in the dripping zone. Therefore, the coke particles in the soft melting zone and especially in the dripping zone have a larger diameter in these areas (because less coke is consumed by direct reduction reactions). Please refer to Table 4, which shows the coke redistribution in different cases. The larger the diameter, the higher the void fraction. As a result, the dimensionless pouring density will be reduced.

[0191] It is well known that at lower values ​​of dimensionless injection density, the dimensionless pressure drop may be higher.

[0192] Coming back to the pressure drop, therefore Directly depends on the gas phase.

[0193] In fact, this parameter is usually calculated with the help of Ergun's equation:

[0194]

[0195] The first term of the equation is a laminar term, which can be neglected under the conditions of the soft melting zone and the dripping zone compared to the second term (ie, the turbulent term).

[0196] Therefore, as a good approximation, we can write:

[0197]

[0198] As already discussed, the particle diameter (D P ) and the void fraction (ε) will be affected by H 2 and the positive impact of high flux and concentration of CO.

[0199] Therefore, always in the safe case, the relationship can be further simplified to:

[0200]

[0201] The worst case occurs in the inlet from the dripping zone to the soft melting zone when the coke ratio is reduced, because the free passage rate of gas here is the lowest. The velocity of gas through the soft melting zone can be estimated as the gas volume flow rate divided by the free cross-sectional area of ​​the coke layer in the soft melting zone, thus:

[0202]

[0203] It can be said very approximately that, especially when the thickness of the coke layer remains constant, the free cross-sectional area is proportional to the coke ratio, so that

[0204]

[0205] The embodiments of the present invention are as follows:

[0206] It is known that blast furnaces have been successfully operated with coke ratios below 210 kg / t HM using higher pulverized coal injection rates fed by highly oxygen-enriched blast (hot air).

[0207] The oxygen consumes / burns the injected coal and coke, thereby providing energy to heat the tuyere gases to the high temperature levels required to melt the reduced ore in the raceway.

[0208] To reduce CO from blast furnaces 2 emissions, the inventors wish to eliminate the need for coal injection and to reduce the coke ratio as much as possible.

[0209] For this reason, the total amount of oxygen injected into the tuyere should be reduced to a low level, preferably below 120 Nm 3 / tHM, preferably less than 112Nm 3 / t HM.

[0210] In order to provide energy for melting the reduced ore at high temperature levels, the volume flow of the tuyere gas can only be slightly reduced, by about 20% if typical cyclotron temperatures of 1800°C to 2600°C are to be maintained.

[0211] Since, in the process variant according to the invention, the reducing gas is no longer generated in the raceway of the blast furnace, or is generated at least only to a small extent, the reducing gas has to be generated externally and supplied to the furnace.

[0212] Table 4 shows the total mass flow rate injected into the furnace for all the cases studied. 2 The composition of the gas injected into the tuyere in all cases is listed in Table 6.

[0213] In order not to exceed acceptable fluid dynamic conditions in the soft melting zone, we therefore propose that this goal can only be achieved if the mass flow rate of the reducing gas injected at the tuyere is kept below 800 kg / t HM, such as below 700 kg / t HM (see Table 5).

[0214] To achieve this, the hydrogen content in the gas injected at the tuyere level must be higher, such as 30%. 2 (100%) case, the total mass flow rate is lower than our case, but the coke is as high as 274 kg / t HM and 324 kg / t HM.

[0215] Table 5: Total mass of gas injected into the tuyere

[0216]

[0217]

[0218] Table 6: Gas components in the reducing gas injected into the tuyere.

[0219]

[0220] In order to estimate the effect of this lower coke ratio on the soft melting zone in terms of pressure drop, it is necessary to know the parameters of the gas entering the soft melting zone. This gas is the gas injected into the tuyere, the coke combustion (if O is injected) 2 ), coke gasification at the tuyere (if H 2 O and CO 2 ) and the product of CO (FeO(l)+C(s)→Fe(l)+CO)) produced by the final reduction reaction in the liquid state.

[0221] In the case of new furnaces (Case 7 and Case 8), the reduction rate of iron ore is almost 100%, which is mainly achieved by the high reducing power of the gas injected into the furnace body and tuyere, while the amount of reduction by final reduction and coke combustion is limited. Therefore, for the new blast furnace, the volume of gas flowing through the soft melting zone is significantly lower.

[0222] Table 7: Bosh gas flow conditions through the CZ and estimated pressure drop for all cases.

[0223]

[0224]

[0225] To estimate the pressure drop across the CZ, the inventors assumed that the ore layer is impenetrable. In addition, it is believed that a portion of the molten slag will penetrate into the coke layer in the CZ, thereby blocking part of its height. Therefore, this coke-ore interface layer is also considered to be an impermeable thickness. Therefore, all rising gases can only flow through the remaining thickness of the CZ coke layer (i.e., total coke layer height-coke-ore interface layer height).

[0226] Therefore, for an operating BF, the thickness of the coke layer excluding the interface layer is typically about 15 cm (case 1 and case 2). The thickness of the coke-ore interface layer is assumed to be about 4 cm. Since the (effective) coke layer thickness is an important factor for stable furnace operation, this value is preferably kept constant in all cases.

[0227] As mentioned previously, the pressure drop depends on the density and velocity (volume flow and composition) of the rising gas.

[0228] As can be seen from Table 4, the pressure drop in the CZ of Case 2 is higher than that of Case 1 due to the lower coke ratio.

[0229] The new furnace with a coke rate of 180 kg / t HM can be run well because the bosh gas can flow more smoothly through the CZ. Nevertheless, it seems challenging to reduce the coke rate to the final value of 100 kg / t HM in the case without shaft injection because the pressure drop in the CZ is quite high. This means that the risk of flooding is high for Case 6.

[0230] This problem can be overcome by increasing the blast pressure. Higher blast pressure increases density and reduces the volume of gas entering the furnace. Velocity has a much greater effect on pressure drop than density because pressure drop is related to the square of velocity, i.e. (See equation (5)). However, higher pressures require more expensive mechanical devices and higher electrical energy requirements.

[0231] However, this challenge can be mitigated by shaft injection, which reduces the volume flow of gas injected into the tuyere, resulting in a lower pressure drop. It can be clearly seen that the pressure drop in Case 8 (new furnace) is even lower than that in Case 2.

[0232] Furthermore, the productivity can be increased due to the reduced pressure drop in the CZ and drip zone of the new furnace. To achieve the pressure drop level in the conventional BF (Case 2), the productivity can be increased by 15%. Thus, the advantages of shaft spraying are again demonstrated in Case 8.

[0233] Table 8 below shows the pressure drop for Case 8 at lower and higher production rates.

[0234]

[0235] Electric heating

[0236] An electrically driven heater can be used to efficiently heat the (first) reducing gas and reach the required temperature for entering the smelting furnace. Advantageously, a gas in a plasma state can be used as a heating means.

[0237] Electrode-based plasma torches can be used as electrically driven heaters. Plasma ignites on the surface of at least two electrodes. The electrodes can be made of graphite. At least one electrode is at a high potential and at least one electrode is at a low potential. DC and three-phase AC plasma torches are electrode-based plasma torches.

[0238] In addition to electrode-based plasma torches, there are also electrodeless plasma torches. In an electrodeless plasma torch, the plasma is ignited by induction, so no electrodes are required. Typical electrodeless plasma torches are microwave (MW) plasma and radio frequency (RF) plasma. RF plasma is often referred to as inductively coupled plasma (ICP).

[0239] Direct current (DC) plasma torches have a smaller volume footprint.

[0240] Alternating current (AC) plasma torches, especially three-phase AC plasma torches, have a larger volume footprint, but have other advantages: The plasma is confined to the ignition area, allowing for better control of the location of the plasma. Due to the alternating current and the resulting cyclical mode of operation, the electrodes cool naturally, which limits electrode erosion and extends electrode life. AC plasma torches do not require swirling gas or magnetic coils to stabilize the plasma as DC plasma torches do, so the torch design is less complex.

[0241] The DC plasma torch may include 2 electrodes or multiples of 2 electrodes (e.g., 2, 4, 6, 8, 12, 14, 16, 18, 20 electrodes). A greater number of electrodes may improve the controllability of the plasma and increase the power of the plasma torch.

[0242] An AC plasma torch, in particular a three-phase AC plasma torch, may include 3 electrodes or multiples of 3 electrodes (e.g., 3, 6, 9, 12, 15, 18, 21 or more electrodes). A greater number of electrodes may improve the controllability of the plasma and increase the power of the plasma torch.

[0243] Plasma torches with a power of 1 MW-10 MW, preferably 2 MW-6 MW, most preferably 4 MW-5 MW, in particular DC plasma torches and / or AC plasma torches and / or three-phase AC plasma torches can be used in the furnace as defined above.

[0244] The plasma torch may be integrated with one or more gas injectors.

[0245] Preferably, one power supply powers 1-10, 1-5, 1-3 or 1 plasma torch of the at least one plasma torch.

[0246] In order to achieve stable plasma operation, the power supply can be designed to have a spare capacity. The spare capacity can be up to 3 times, preferably 2 times or even 1.5 times the plasma power required to operate the plasma torch. It is more preferred to use a single power supply with a total capacity equal to or higher than the sum of the capacities of all low-capacity power supplies to power multiple plasma torches using multiple power supplies less than 30MW, less than 20MW and / or less than 10MW. The flicker caused by the fluctuation of plasma torch operation on the power grid in the former case is far less serious than the latter case. In addition, the use of multiple <30MW, 20MW or 10MW power supplies provides better controllability and flexibility: when the power supply fluctuates or collapses, the entire system will not be disturbed by the propagation, and the furnace can remain in operation without serious problems because other power supplies can jointly provide the power input of the collapsed power supply. In addition, one or more backup power supplies can be installed online, and in the event of a failure of the main power supply, switching to the backup power supply ensures steady-state operation at full power. During the next scheduled maintenance shift, maintenance can be carried out, so that production losses will never occur. However, a large number of power supplies results in higher costs, higher power losses, and higher space requirements, so an optimal number of power supply units should be selected.

[0247] In an AC plasma torch, particularly in a three-phase AC plasma torch, the electrode may be rod-shaped. When the plasma is turned on, one side of the electrode arranged in the plasma ignition region is eroded and the length of the electrode is shortened. The plasma torch is equipped with a mechanism that ensures that the inter-electrode gap at the plasma ignition region remains constant by moving the electrode inward toward the plasma ignition region. After reaching a predetermined minimum length, the mechanism can replace or modify the electrode. In some embodiments, the inter-electrode gap can be adjusted to between 0 mm and 100 mm, for example, between 5 mm and 50 mm or about 40 mm.

[0248] Modification of the electrode is accomplished by screwing a new electrode on the back side of the old / used electrode (opposite the side of the electrode arranged in the plasma ignition zone). Attachment of the new electrode to the old electrode is accomplished by an electrode clamping device while the welding torch is in operation.

[0249] When plasma operation causes graphite electrodes to gradually erode and be consumed, another possibility for modifying the electrodes may be the use of a carbon-based paste. A carbon paste, typically a mixture of graphite and a binder, may be applied to the consumed or worn portion of the electrode. This paste replenishes the carbon content, extends the life of the electrode, and helps maintain effective conductivity and heat transfer during plasma operation. A device designed to modify the electrode without interrupting the plasma process can typically be used to add a carbon paste to modify the graphite electrode by bringing a column of electrode paste to the consumed portion of the graphite electrode. The device containing the carbon-based paste gradually pushes the paste into the electrode column to fill the voids left by the consumed electrode material and restore the carbon content, thereby enabling controlled and precise addition of the carbon paste and ensuring that the performance and efficiency of the electrode are maintained throughout the plasma operation, thereby helping to extend the operating life of the electrode and improve the overall effectiveness of the plasma operation.

[0250] In a DC plasma torch, the electrode may have a tubular shape. During operation, one side of the tube at the plasma ignition region is eroded and the thickness of the electrode becomes thinner. The plasma torch electrode replacement device replaces a broken electrode in a plasma torch with a new electrode. Replacing a used electrode with a new electrode is achieved by another electrode clamping device.

[0251] The mechanism of the electrode replacement system may be equipped with a magazine for new electrodes and a magazine for used electrodes, so the plasma torch can be operated for a long time without human interaction.

[0252] In a DC plasma torch, the plasma is controlled by adjusting electrical operating parameters. In a three-phase AC plasma torch, plasma control is based on a camera that continuously captures images of the plasma. Using relevant software, the plasma characteristics depicted in these images (i.e., brightness, shape, diffusivity, etc.) are benchmarked against plasma images depicting the characteristics of the plasma in a steady state. Then, changes (i.e., inter-electrode gap, voltage amplitude, etc.) are applied to maintain the plasma in a steady state.

[0253] In some embodiments, the gas velocity flowing through the plasma heater including the plasma torch can be between 10m / s and 120m / s, preferably between 20m / s and 50m / s. The incoming gas flow reaching the plasma heater can be divided into at least two streams, the first stream flowing through the arc generated by the plasma torch in the center, and the second stream flowing around the arc at the periphery. Both streams can have substantially the same speed and / or flow dynamics. However, it is preferred that the two streams have different speeds and flow dynamics, such as the central stream flowing through the arc is preferably a low-speed stream (5m / s to 60m / s), wherein the turbulence is as small as possible, and the peripheral stream is preferably a high-speed stream (30m / s to 200m / s), and can be set as a vortex.

[0254] In some preferred embodiments, the core stream flows through the plasma arc and is heated to a very high temperature. The second stream is injected a short distance downstream of the plasma arc and is oriented so that it acts to protect the refractory lining wall of the plasma combustion chamber of the plasma torch from the heat of the core high temperature stream, thereby advantageously reducing the heat load on the wall lining.

[0255] Detailed Description of Embodiments

[0256] Figure 1 Advantageous embodiments of a smelting furnace facility according to aspects of the invention are presented (such as a blast furnace facility modified to be able to operate according to the invention).

[0257] The (modified) blast furnace facility comprises a blast furnace 10 having conventional tuyeres and tuyere branches 21 supplied by a bosh duct 20. However, unlike a conventional blast furnace, the bosh duct 20 supplies the blast furnace 10 with a first reducing gas A via the tuyere branches 21 and the tuyeres. In addition, a second reducing gas B is supplied at the shaft level by a plurality of injectors (not shown) supplied by an annular duct 25.

[0258] The first reducing gas A and the second reducing gas B preferably comprise reformed gas obtained by reforming the top gas D of a blast furnace or other gases from a metallurgical plant. 2is added to the second reducing gas B specifically for increasing the hydrogen content in the second reducing gas or for adjusting the temperature of the second reducing gas, such as cooling the second reducing gas to a desired temperature. 2 O and / or natural gas (NG) or any other suitable source, in any suitable reformer 40 or device operated in this manner (e.g., Figure 1 Hydrogen can be added to the reformer 40 if necessary.

[0259] Prior to reforming, the top gas D is preferably cleaned in a top gas cleaner 50 to remove any solid particles, thereby providing cleaned top gas C. If desired, the top gas D or the cleaned top gas C may be subjected to further treatment steps before entering the reformer 40, e.g. to (partially) remove specific components, such as H 2 O, chlorine, heavy metals, sulfur components (such as COS), etc. The purified top gas C can also be added to the second reducing gas B directly (ie without reforming).

[0260] The first reducing gas A is heated to a temperature of more than 1600° C. before passing through the tuyere via the tuyere branch pipe 21 and being injected into the blast furnace 10. This (additional) heating (or partial heating) can be performed by a (resistance) heating device 30 before entering the bosh pipe 20. However, it is preferred that the first reducing gas A is heated to the required temperature only shortly before being injected into the blast furnace 10, for example by a plasma torch (not shown) mounted on the tuyere branch pipe 21 (such as on the blowpipe).

[0261] According to the invention, a small amount of oxygen E may be added at the tuyere level, such as for forming and maintaining a raceway gap at the tuyere 21 in the blast furnace 10. The oxygen E is preferably injected via a corresponding oxygen port (not shown) arranged in the tuyere. The oxygen E is preferably added at a relatively low temperature (compared to the first reducing gas) so as to be able to cool the tuyere 122 ( Figure 2 ). The oxygen addition can be carried out by means of a dedicated oxygen lance or, alternatively, by means of an oxygen port directly integrated in the tuyere or blowpipe and in particular in the nose thereof.

[0262] Figure 2 A possible embodiment of an electric heater that can be used in the context of the present invention is generally presented. In this embodiment, three electrode plasma torches 1213 (due to the cross-sectional view, only two plasma torches are shown) are arranged in the blowpipe 1211 of the tuyere branch 121 so that their electrodes 1214 reach the central pipe of the blowpipe 1211, which preferably includes a refractory lining 1212. Figure 2In the embodiment, the tuyere branch pipe 121 is fluidly connected to a tuyere 122 located in the wall (not shown) of the smelting furnace, and the nose 1221 of the tuyere 122 reaches into the smelting furnace. Advantageously, an oxygen port 1222 is arranged in the tuyere 122 device for injecting oxygen (preferably cold oxygen), as further disclosed above.

[0263] Figure 3 A schematic (half) cross section of an operating blast furnace is shown, comprising superimposed layers of coke and iron ore fed from the furnace roof. Figure 3 A detailed view of the various layers within the soft melting zone is also shown. The first reducing gas A is injected at the tuyere level, and due to the velocity of the gas and the direct gasification of the coke, a whirlpool zone is formed. The generated gas rises in the furnace and has to flow through the coke layer in the soft melting zone, wherein the now softened and molten iron (ore) layer in the soft melting zone becomes substantially impermeable to gases. The injection of the second reducing gas B pushes the rising gas towards the center of the furnace, thereby largely preventing the above-mentioned wall channeling effect.

[0264] Reference numerals list

[0265] 10. Blast Furnace

[0266] 20 Bosh pipe of the first ejector device

[0267] 21 Tuyere branch pipe of the first ejector device

[0268] 25 Annular pipe of the second ejector device

[0269] 30 Heating unit

[0270] 40 Reformer

[0271] 50 Top gas cleaning unit

[0272] A. First reducing gas

[0273] B Second reducing gas

[0274] C Purified top gas

[0275] D Top gas EO 2

[0276] 121 Air outlet branch pipe 1211 Blowpipe

[0277] 1212 Refractory lining 1213 Plasma Torch 1214 Electrode

[0278] 122 vent

[0279] 1221 Nose 1222 Oxygen port

Claims

1. A method for operating a smelting furnace facility, in particular, the smelting furnace facility is a blast furnace facility, the method comprising: - supplying coke, iron oxides and other iron-containing materials and, if necessary, fluxes to the roof of the smelting furnace, - injecting a first reducing gas containing hydrogen at a temperature above 1600° C. at the tuyeres level of the smelting furnace, - injecting oxygen at the level of the tuyere of the smelting furnace, preferably at a temperature below 600°C, more preferably below 400°C, and - injecting a second reducing gas at the level of the lower furnace body of the smelting furnace, wherein the coke is supplied at a lump coke ratio of less than 220 kg / t HM, preferably less than 200 kg / t HM and more preferably less than 180 kg / t HM, and wherein the oxygen flow rate injected at the tuyere level is less than 120 Nm 3 / t HM, preferably less than 112Nm 3 / t HM.

2. The method according to claim 1, wherein: The first reducing gas is injected at the tuyere level with a total mass flow rate below 800 kg / t HM, preferably below 775 kg / t HM and more preferably below 750 kg / t HM.

3. The method according to any one of claims 1 or 2, wherein: The density of the first reducing gas is lower than 0.80 kg / Nm 3 , preferably less than 0.60kg / Nm 3 And most preferably less than 0.30kg / Nm 3 .

4. The method according to any one of claims 1 to 3, wherein: The first reducing gas and / or the second reducing gas contain gas produced by a reforming process. Specifically, the reforming process is to reform coke oven gas, natural gas, biogas and / or other hydrocarbon-containing gases using H2O, CO2 or a gas containing CO2 and / or H2O, and more preferably, to reform coke oven gas, natural gas, biogas and / or other hydrocarbon-containing gases using steel plant waste gas such as smelter top gas, alkaline oxygen converter gas and / or open bath furnace gas.

5. The method according to any one of claims 1 to 4, wherein: The first reducing gas and / or the second reducing gas comprises gas produced by applying CO2 separation technology such as monoethanolamine (MEA) absorption, membrane separation, pressure swing adsorption (PSA) or vacuum pressure swing adsorption (VPSA) to hydrogen and / or CO rich gases, more preferably to steel plant gases such as smelter top gas, alkaline oxygen gas and / or oxygen blast furnace gas.

6. The method according to any one of claims 1 to 5, wherein: The first reducing gas has a hydrogen content higher than 30% by volume, preferably higher than 40% by volume, more preferably higher than 50% by volume.

7. The method according to any one of claims 1 to 6, wherein: The first reducing gas is injected at a temperature of 1600 to 2600°C, more preferably at a temperature above 1800°C and most preferably at a temperature above 2000°C.

8. The method according to any one of claims 1 to 7, wherein: Before spraying the first reducing gas into the smelting furnace, the first reducing gas is heated by one or more electric heaters, preferably in one or more tuyere branches and / or one or more tuyere, most preferably by one or more plasma torches.

9. The method according to claim 8, wherein: The first reducing gas is heated by one or more plasma torches arranged in the blowpipe of one or more of the tuyere branches, wherein the plasma torch is preferably an electrode-based plasma torch or an electrodeless plasma torch, and the electrodeless plasma torch is selected from a plasma torch such as a plasma torch ignited by induction, a microwave plasma torch, a radio frequency plasma torch or a combination thereof.

10. The method according to claim 9, wherein: One or more of the plasma torches are DC plasma torches and / or AC plasma torches and / or three-phase AC plasma torches, wherein the plasma torches have a rated electrical power of 1 MW to 10 MW, preferably 2 MW to 6 MW, most preferably 4 MW to 5 MW.

11. The method according to any one of claims 1 to 10, wherein: The first reducing gas and / or the second reducing gas has a molar ratio (H2+CO) / (H2O+CO2) higher than 6, preferably higher than 7 and more preferably higher than 8.

12. The method according to any one of claims 1 to 11, wherein: The second reducing gas has a hydrogen content higher than 25% by volume, preferably higher than 30% by volume, more preferably higher than 40% by volume.

13. The method according to any one of claims 1 to 12, wherein: The second reducing gas is injected at a temperature of 800 to 1200°C, more preferably at a temperature below 1100°C and most preferably at a temperature below 1000°C.

14. The method according to any one of claims 1 to 13, wherein: The pressure level of the smelting furnace at the tuyere level is controlled to a value higher than 2 barg, preferably higher than 4 barg and more preferably higher than 5 barg.

15. The method according to any one of claims 1 to 14, wherein: The first reducing gas and the second reducing gas have a nitrogen content lower than 35% by volume, preferably lower than 15% by volume, more preferably lower than 10% by volume and most preferably lower than 5% by volume.

16. The method according to any one of claims 1 to 15, wherein: The first reducing gas and / or the second reducing gas contains a gas generated by cracking ammonia.

17. The method according to any one of claims 1 to 16, wherein: The coke is supplied in layers, and wherein the height of each coke layer is at least 10 cm, preferably at least 12 cm, more preferably at least 15 cm.

18. The method according to any one of claims 1 to 17, further comprising the steps of: The amount and / or component of the second reducing gas injected at the level of the furnace body is controlled according to the amount and / or component of the first reducing gas injected at the level of the tuyere and / or the amount of oxygen injected at the level of the tuyere, thereby adjusting the average reduction degree of the iron-oxide-containing material reaching the soft melting zone to a value higher than 85%.

19. The method according to any one of claims 1 to 18, further comprising the steps of: The top pressure of the smelting furnace is controlled within the range of 1 barg to 10 barg, more preferably within the range of 2 barg to 7 barg and most preferably within the range of 3 barg to 5 barg, so as to reduce channel effect and overflow effect.

20. The method according to any one of claims 1 to 19, further comprising the steps of: The wall channel effect of the gas from the soft melting zone is reduced by controlling the injection conditions of the second reducing gas, such as the injection speed and / or flow rate of the second reducing gas injected into the furnace body of the smelting furnace.

21. The method according to any one of claims 1 to 20, further comprising the steps of: The carbon dioxide content of any one or more of the carbon dioxide-containing waste gases and / or process gases generated during operation is reduced by carbon capture and utilization (CCU) and / or carbon capture and storage (CCS).

22. The method according to any one of claims 1 to 21, further comprising the steps of: The carbon dioxide in any one or more of the carbon dioxide-containing waste gases produced during operation is converted to synthetic fuels, such as to synthetic natural gas by methanation or to methanol and / or ethanol by methanol and / or ethanol production.

23. A smelting furnace facility, in particular a blast furnace facility, comprising: - a charging device configured for feeding coke, iron-containing oxides and other iron-containing materials and, if necessary, fluxes to the roof of the smelting furnace, - a first injector device, located at the tuyere level of the smelting furnace and configured for injecting a first reducing gas containing hydrogen at a temperature above 1600° C. at the tuyere level of the smelting furnace, - a second injector device, located at the level of the shaft of the smelting furnace and configured to inject a second reducing gas at the level of the lower shaft of the smelting furnace, - oxygen injection port means, configured for injecting oxygen at the level of the tuyere of the smelting furnace, wherein the charging device is configured to supply coke at a lump coke ratio of less than 220 kg / t HM, preferably less than 200 kg / t HM and more preferably less than 180 kg / t HM; wherein the first injector device comprises an electric heating device, the electric heating device being configured to heat the first reducing gas to the above-mentioned temperature of more than 1600° C.; and wherein the oxygen injection port is configured to inject the first reducing gas at a rate of less than 120 Nm 3 / t HM, preferably less than 112Nm 3 Oxygen is injected at a flow rate of / t HM, wherein the temperature of the injected oxygen is preferably lower than 600°C and more preferably lower than 400°C.

24. The smelting furnace facility according to claim 23, wherein: The oxygen injection port arrangement is arranged within the first injector arrangement.

25. The smelting furnace facility according to claim 23 or 24, wherein: The smelting furnace facility is configured to provide a density of less than 0.80 kg / Nm 3 , preferably less than 0.60kg / Nm 3 , most preferably less than 0.30kg / Nm 3 of the first reducing gas.

26. A smelting furnace installation according to claims 23 to 25, said first injector arrangement being configured for injecting said first reducing gas at said tuyere level at a total mass flow rate below 800 kg / t HM, preferably below 775 kg / t HM and more preferably below 750 kg / t HM.

27. The smelting furnace facility according to claims 23 to 26, further comprising one or more reformers, wherein the one or more reformers are configured to produce gas as the first reducing gas and / or the second reducing gas through a reforming process, specifically, the reforming process is to reform coke oven gas, biogas, natural gas and / or other hydrocarbon-containing gases using H2O and / or CO2 or using gases containing CO2 and / or H2O, and more preferably to reform coke oven gas, biogas, natural gas and / or other hydrocarbon-containing gases using steelmaking waste gases such as smelting furnace top gas, alkaline oxygen converter gas, open bath furnace gas, etc.

28. The smelting furnace facility according to claims 23 to 27, further comprising one or more devices configured to separate CO2 through a CO2 separation process such as monoethanolamine (MEA) absorption, membrane separation, pressure swing adsorption (PSA) or vacuum pressure swing adsorption (VPSA), for treating smelting furnace top gas, basic oxygen converter gas and / or open bath furnace gas.

29. The smelting furnace facility according to claims 23 to 28, further comprising a first hydrogen source and a first hydrogen content controller, wherein the first hydrogen content controller is configured to adjust the hydrogen content in the first reducing gas to a value higher than 30 volume %, preferably higher than 40 volume %, and more preferably higher than 50 volume %.

30. A smelting furnace facility as claimed in claims 23 to 29, wherein: The electric heating arrangement of the first injector arrangement is configured for heating the first reducing gas to a temperature of 1600 to 2600°C, more preferably to a temperature above 1800°C and most preferably to a temperature above 2000°C.

31. A smelting furnace facility according to claims 23 to 30, wherein: The electrical heating device comprises one or more electrical resistance heaters and / or one or more plasma torches.

32. The smelting furnace facility according to claim 30, wherein: The electric heating device comprises one or more plasma torches arranged in the blowpipe of one or more tuyere branches, the plasma torches are preferably electrode-based plasma torches or electrodeless plasma torches, the electrodeless plasma torches are selected from plasma torches such as those ignited by induction, microwave plasma torches, radio frequency plasma torches or combinations thereof.

33. The smelting furnace facility according to claim 32, wherein: One or more of the plasma torches are DC plasma torches and / or AC plasma torches and / or three-phase AC plasma torches, wherein the plasma torches have a power of 1 MW to 10 MW, preferably 2 MW. The rated electrical power is from 4MW to 5MW, preferably from 6MW to 6MW.

34. The smelting furnace facility according to claims 23 to 33, further comprising a second hydrogen source and a second hydrogen content controller, wherein the second hydrogen content controller is configured to adjust the hydrogen content in the second reducing gas to above 25 volume %, preferably above 30 volume %, and more preferably above 40 volume %.

35. A smelting furnace facility according to claims 23 to 34, wherein: The first injector device comprises an upstream regulating device, which is configured to control the mass flow rate of the reducing gas injected into the smelting furnace at the tuyere level to 800 kg / t HM, preferably below 775 kg / t HM and more preferably below 750 kg / t HM at a pressure level above 2 bar gauge, preferably above 4 bar gauge and more preferably above 5 bar gauge.

36. The smelting furnace facility according to claims 23 to 35, further comprising a regulating unit, which is configured to control the amount and / or component of the second reducing gas injected through the second injector device at the furnace body level according to the amount and / or component of the first reducing gas injected at the tuyere level and / or the amount of oxygen injected through the oxygen injection port at the tuyere level, so as to adjust the average reduction degree of the iron-oxide-containing material reaching the soft melting zone to a value higher than 85%.

37. The smelting furnace facility according to claims 23 to 36 further comprises a carbon capture and utilization (CCU) unit and / or a carbon capture and storage (CCS) unit located downstream of at least one carbon dioxide-containing exhaust gas generating element for reducing the carbon dioxide content in the exhaust gas.

38. A smelter facility according to claims 23 to 37, further comprising a methanation unit configured for converting carbon dioxide into synthetic natural gas and / or process gas or any other device for producing synthetic hydrocarbons such as methanol and ethanol.

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