AU2022284294A1

AU2022284294A1 - Method for operating a blast furnace installation

Info

Publication number: AU2022284294A1
Application number: AU2022284294A
Authority: AU
Inventors: Gilles Kass; Klaus Peter KINZEL; Miriam VALERIUS
Original assignee: Paul Wurth SA
Current assignee: Paul Wurth SA
Priority date: 2021-06-03
Filing date: 2022-06-02
Publication date: 2023-12-07
Also published as: KR20240016962A; LU500245B1; CN117377778A; WO2022253938A1; BR112023024416A2; EP4347897A1; TW202336237A

Abstract

A method for operating a blast furnace is presented, said method comprising the steps of collecting a stream of blast furnace gas from the blast furnace; feeding said stream of blast furnace gas and a hydrocarbon containing gas to a reforming plant comprising at least one reformer; reforming said stream of blast furnace gas and said hydrocarbon containing gas in the reforming plant to produce a stream of syngas; and feeding at least a portion of said stream of syngas to the blast furnace; wherein a stream of h½ is added to the hydrocarbon containing gas before step (c) and/or to the stream of blast furnace gas before step (c) and/or to the stream of syngas before step (d) and/or to the tuyere of the blast furnace, wherein the feeding of at least a portion of said stream of syngas to the blast furnace occurs through the shaft of the blast furnace and/or through the tuyere of the blast furnace, and wherein the utilization efficiency of the hydrogen in a blast furnace plant comprising the blast furnace, the reforming plant and a cowper plant is above 60%.

Description

METHOD FOR OPERATING A BLAST FURNACE INSTALLATION Technical field

[0001 ] The present invention generally relates to a method for operating a blast furnace installation as well as to such a blast furnace installation.

Background Art

[0002] Despite alternative methods, like scrap melting or direct reduction within an electric arc furnace, the blast furnace today still represents the most widely used equipment for the production of steel. One of the concerns of a blast furnace is the blast furnace gas (BFG) exiting the top of the blast furnace, commonly also referred to as "top gas". While, in the early days, this top gas may have been allowed to simply escape into the atmosphere, this has later been avoided by using it in BFG fed power plants in order not to waste the energy contained in the gas and cause an undue burden on the environment. One component in the blast furnace gas is CO2, which is environmentally harmful and is mainly useless for industrial applications. Indeed, the waste gas exiting the power plant fed with the blast furnace gas typically comprises a concentration of CO2 as high as 20 vol% to 40 vol%. The blast furnace gas being combusted usually comprises besides the before mentioned CO2 considerable amounts of N2, CO, H2O and H2. The N2 content, however, largely depends on whether hot air or (pure) oxygen is used for the blast furnace.

[0003] Mainly in order to reduce the amount of coke or other carbon sources used, a suggestion was made to recover the blast furnace gas from the blast furnace, treat it to increase its reduction potential and to inject it back into the blast furnace to aid the reduction process. One method for doing this is reducing the CO2 content in the blast furnace gas by Pressure Swing Adsorption (PSA) or Vacuum Pressure Swing Adsorption (VPSA), such as disclosed in patent application EP 2 886 666 A1 . Although PSAA/PSA installations allow a considerable reduction of the CO2 content in the blast furnace gas from about 40% to about 5%, they are very expensive to acquire, to maintain and to operate and further they need a lot of space.

[0004] It has also been proposed to use the blast furnace gas as a reforming agent for hydrocarbons in order to obtain a synthesis gas (also referred to as syngas) that can be used for several industrial purposes. According to a proposed reforming process, the blast furnace gas is mixed with a carbonaceous gas that contains at least one hydrocarbon (e.g. lower alkanes). In a so-called dry reforming reaction, the hydrocarbons of the gas react with the CO2 in the blast furnace gas to produce H2 and CO. At the same time the hydrocarbons react with the H2O in the blast furnace gas also producing H2 and CO by so called steam reforming reaction.

[0005] In the context of the reduction of CO2 emissions, considerable efforts are also being made to reduce the usage of carbonaceous fuel for the operation of the blast furnace itself. As a replacement, fuels with increased hydrogen content, in form of hydrocarbons, gaseous hydrogen H2 or a mixture thereof, are used. Hydrogen and hydrocarbons being rich in calorific value, have the potential for injection in blast furnace tuyere as an auxiliary fuel. The higher the participation of the hydrogen in the bosh and shaft gas, generally the higher is the CO2 reduction potential for the blast furnace operation. The “bosh gas” commonly corresponds to gas in the cohesive zone of the blast furnace, while “shaft gas” in the present context corresponds to the gas injected in the shaft of the blast furnace i.e. above the cohesive zone.

[0006] However, injection of cold H2 and/or hydrocarbons at the tuyere level / through the tuyere along with high amount of pulverized coal (PCI) leads to a significant drop in the RAFT (raceway adiabatic flame temperature). In order to increase the RAFT, higher oxygen enrichment is required being limited by the top gas temperature. Therefore, only a relatively small amount of cold H2 and/or hydrocarbons can be injected into the blast furnace through the tuyeres, which limits the CO2 saving potential of this technology.

[0007] Injection of hot hydrogen or even injection of hot hydrocarbons, such as natural gas at the tuyere level / through the tuyere may allow higher amounts of hydrogen utilisation as well as higher CO2 saving from the blast furnace. However, the production of hot hydrogen and especially of hot hydrocarbons is not technically simple, since hydrocarbons tend to crack at higher temperatures and steel tends to decarburize when in contact of hot hydrogen, making the steel prone for cracking.

[0008] Moreover, when injecting hydrocarbons and/or hydrogen in the blast furnace only part of the hydrogen is used in the blast furnace for the reduction of the iron ore while the remainder leaves the blast furnace with the top gas, further limiting the benefits of hydrogen and/or hydrocarbon injection. The percentage of hydrogen consumption in the blast furnace gets worse when increasing the amount of hydrogen in the blast furnace resulting from the injection of hydrocarbons and/or hydrogen. This means that the potential of CO2 emission reduction for a given quantity of hydrogen decreases when using increasing amounts of hydrogen in the blast furnace.

[0009] The last point is especially problematic when the hydrogen injected in the blast furnace is a renewable hydrogen produced from electricity with an electrolysis process. In fact, using a portion of the blast furnace gas leaving the blast furnace plant in a thermal power plant results typically in a low thermal efficiency of approximately 25 to 35%. This means that 65 to 75% percent of the energy of this portion of the blast furnace gas is lost when being used for the production of electric power. It is thus evident that especially in the case of utilisation of expensive carbon lean energy sources, such as hydrogen, in the blast furnace plant, the utilisation of blast furnace gas for the production of electric energy should be avoided as much as possible.

Technical problem

[0010] It is thus an object of the present invention to provide a new method for operating a blast furnace as well as a corresponding blast furnace plant, allowing for efficient hydrogen utilization in the blast furnace plant, reducing the CO2 emissions resulting from the traditional blast furnace steel making and for at least partially overcoming the above-mentioned problems.

[0011] This object is achieved by a method according to claim 1 and 2 and by a blast furnace installation according to claim 19.

General Description of the Invention

[0012] In order to achieve said object, the present invention proposes, in a first aspect, a method for operating a blast furnace, comprising the steps of

(a) collecting a stream of blast furnace gas from the blast furnace having a shaft and at least one tuyere;

(b) feeding the stream of blast furnace gas and a hydrocarbon containing gas to a reforming plant comprising at least one reformer;

(c) reforming the stream of blast furnace gas and the hydrocarbon containing gas in the reforming plant to produce a stream of syngas; and

(d) feeding at least a portion of the stream of syngas to the blast furnace. [0013] A stream of hh is added to the hydrocarbon containing gas before step (c) and/or to the stream of blast furnace gas before step (c) and/or to a mixture comprising the blast furnace gas and the hydrocarbon containing gas before step (c) and/or to the stream of syngas before step (d). hh addition is performed in order to increase the amount of hh injected (i.e. fed) to the blast furnace. A method according to the invention does not comprise any hh removal step. The feeding of at least a portion of the stream of syngas to the blast furnace occurs at the shaft level / through the shaft of the blast furnace. It is also possible that the feeding of at least a portion of the stream of syngas to the blast furnace occurs at the tuyere level / through a tuyere of the blast furnace or both through the shaft of the blast furnace and through the tuyere of the blast furnace. In other words, in some embodiments, a portion of the stream of syngas is fed at the shaft level and another portion of the stream of syngas is simultaneously fed through the tuyere of the blast furnace, while in other embodiments, the feeding of a portion of the stream of syngas occurs only through the shaft of the blast furnace.

[0014] In embodiments, a further stream of hydrogen and/or hydrocarbons may be added at the tuyere of the blast furnace.

[0015] Although the method could be applied to the production of other metals like lead or copper, the blast furnace is normally used for producing pig iron.

[0016] In the context of the present invention, a syngas refers to a synthesis gas produced by a reforming process in a reformer.

[0017] In the context of the present invention, the reforming plant comprises at least one reformer. In embodiments, the reforming plant may comprise a plurality of reformers, the reformers being arranged in a series or in parallel with regard to each other, or the reforming plant may comprise a plurality of reformers arranged to form at least two series of reformers, the at least two series being arranged in parallel with respect to each other. The reformers of the reforming plant may be of any type, such as e.g. a regenerative reformer or a catalytic dry and/or wet reformer of any type, in particular bottom fired, side fired, terrace type or top fired. In embodiments wherein the reforming plant comprises more than one reformer, reformers may be identical or different from each other. The reforming plant may e.g. comprise a pre-reformer and a main reformer. The exact number, type and arrangement of reformers in the reforming plant could advantageously be adapted depending on the level of subsequent feeding of the produced syngas to the blast furnace in order to meet requirements for the produced syngas (such as e.g. temperature, reduction degree), or depending on the position of the addition of the hydrogen.

[0018] For the reforming process to take place in the reforming plant, as carbon dioxide and steam source, e.g. the collected blast furnace gas, and a hydrocarbon containing gas must be combined (i.e. mixed) to form a gas mixture before or on entering the reaction chamber of the first reformer of the reforming plant. In embodiments wherein the reforming plant comprises only one reformer, the first reformer corresponds to this reformer.

[0019] The gas being reformed in the reactor is a gas mixture of the blast furnace gas and hydrocarbon containing gas and possibly also steam and which can be more or less well mixed. Combining the blast furnace gas with the hydrocarbon containing gas and possibly the steam in general refers to "allowing the blast furnace gas to mix with the hydrocarbon gas and possibly the steam". This may comprise (actively) mixing the blast furnace gas with the hydrocarbon containing gas and possibly the steam, i.e. applying mechanical force to mix the gases. However, in some cases it may be sufficient e.g. to inject the gases into a pipe, so that mixing occurs more or less passively by convection and/or diffusion. It is understood, though, that the chemical reaction is enhanced by a higher degree of mixing. It is possible that the gases are combined and mixed in a dedicated vessel which may be referred to as a mixing vessel or mixing chamber. In embodiments, it might also be sufficient to separately inject the blast furnace gas and the hydrocarbon containing gas and possibly the steam to a reformer and allow the gases to mix inside the reformer e.g. in a pre-chamber of the reformer.

[0020] In an aspect, the present invention also proposes a method for operating a blast furnace plant by improving the efficiency of hydrogen utilization. The method comprises the combination of H2 addition to the blast furnace, with a reforming reaction, wherein the part of hydrogen utilisation in a blast furnace plant comprising the blast furnace, a reform ing plant and a cowper plant is above 60% of the hydrogen fed to the blast furnace and preferably above 65% of the hydrogen fed to the blast furnace, wherein the hydrogen fed to the blast furnace is totalling a flow of minimum 200 Nm³/t of produced hot metal and out of which a minimum of 50Nm³ / 1 of hot metal are fed to the blast furnace plant in form of molecular hydrogen H2. [0021 ] The hydrogen utilisation is defined as: (hydrogen input to the blast furnace plant - hydrogen export from the blast furnace plant) / (hydrogen input to the blast furnace plant).

[0022] The hydrogen input to the blast furnace, or hydrogen fed to the blast furnace, or hydrogen input to the blast furnace plant is defined as the total hydrogen content of the bosh gas (i.e. gas in the cohesive zone of the blast furnace) and of the shaft gas injected to the blast furnace at shaft level. This hydrogen input to the blast furnace includes in particular the hydrogen contained in the syngas, in the injected molecular hydrogen hh, in the other hydrogen containing gases, in the injected coal and/or tar, in the humidity of the injected gases and solid fuels and in the humidity of the hot blast.

[0023] The hydrogen export is defined as the hydrogen contained in the blast furnace gas leaving the blast furnace at its top subtracting its utilization in the cowper plant and if applicable in the reforming plant.

[0024] In another aspect, the present invention proposes a blast furnace plant comprising a blast furnace provided with a shaft, tuyeres arranged for feeding a stream of hydrogen containing gas to the blast furnace and gas inlets in the shaft of the blast furnace arranged for feeding a stream of syngas to the blast furnace, preferably a stream of hot syngas. The blast furnace plant further comprises: a reforming plant comprising at least one reformer in fluidic connection with the top of the blast furnace and with a source of a hydrocarbon containing gas, said reforming plant being arranged for converting a stream of blast furnace gas and the hydrocarbon containing gas to a stream of syngas and being in fluidic downstream connection with said gas inlets in the shaft of the blast furnace; and a source of a stream of hh in fluidic connection with the at least one reformer and/or with the gas inlets in the shaft of the blast furnace and/or the tuyere of the blast furnace.

In embodiments, the reforming plant may also be in fluidic downstream connection with the tuyeres of the blast furnace.

[0025] Advantageously, the blast furnace installation is configured for being operated by implementing a method according to the first aspect and as described more in detail below. [0026] The disclosure thus proposes an integrated method and a corresponding installation allowing for operating a blast furnace with a reduced coke and other carbon source rate, with a smaller CO2 footprint and with an increased efficiency of hydrogen (H2) utilization.

[0027] Indeed, the present inventors have found that by combining hydrogen (H2) utilization, recycling of blast furnace gas with reforming of hydrocarbons, the CO2 emission of a blast furnace installation could be reduced without negatively affecting the quality of the produced metal, e.g. pig iron. One of the major advantages of the present method and installation is thus that by reconditioning part of the blast furnace gas for re-use, the overall CO2 production of the blast furnace operation can be substantially reduced.

[0028] Another major advantage is that by reconditioning part of the blast furnace gas for re-use, the overall energy efficiency of the blast furnace plant, comprising the blast furnace, the reforming plant and a cowper plant, can be increased, thereby improving the efficiency of hydrogen utilization. Added H2 is generally not entirely consumed inside the blast furnace plant, so that at least a part of the added H2 exits the blast furnace plant within the export blast furnace gas. Export blast furnace gas means in the present context the blast furnace gas that is left from the blast furnace gas exiting the blast furnace after its consumption within the blast furnace plant, more specifically after its consumption in the blast furnace, cowper plant and reforming plant. Utilisation of the blast furnace gas in the reforming plant as fuel gas for the burners of the at least one reformer also increases the utilisation of the blast furnace gas within the blast furnace plant. The blast furnace gas being collected and recycled within the blast furnace plant for producing a syngas will be used with a very high overall energy efficiency. Through the reforming it can be directly and indirectly used for metallurgical purposes in the blast furnace instead of being sent to e.g. a thermal power plant. As a consequence, at least a portion of the exiting H2 will not be burned to produce energy at a low energy efficiency rate, e.g. electricity. In other words, there is less energy wasted due to H2 burning, and the overall energy efficiency of H2 utilization is improved.

[0029] Indeed, production of hydrogen often requires a large amount of energy and occurs with a production efficiency of about 60%. When injecting hydrogen in the blast furnace only part of the hydrogen is used for the reduction of the iron ore inside the blast furnace. Generally, between 30 and 55% of the added hydrogen is used for this iron ore reduction, the remainder leaves the blast furnace within the top gas. Burning the hydrogen contained in the blast furnace top gas will produce electric energy with a production efficiency of about 30%. This results in the “destruction” of 59 to 69% of the electric energy used for the production of this part of the hydrogen.

[0030] Collecting hydrogen at the top of the blast furnace and re-using it in the blast furnace plant with the help of the highly efficient, typically above 80%, reforming technology reduces the proportion of the hydrogen being used in the power plant and thus the proportion of energy destruction.

[0031] Furthermore, the injection of the resulting syngas at the shaft level of the blast furnace allows for a significant reduction of the coke rate, i.e. the amount of coke and/or other carbon source per ton of pig iron produced.

[0032] Additionally, the injection of syngas in the shaft of the blast furnace is allowing a higher tuyere injection of pulverized coal, of natural gas, and especially also of hydrogen, or of other materials. Thus, extra amounts of coke can be replaced by hydrogen rich auxiliary fuels allowing to further reduce the carbon content of the blast furnace reductant and consequently the CO2 emissions.

[0033] Nevertheless, higher auxiliary injection rates lead to even lower hydrogen utilization requiring even more blast furnace gas recirculation. This problem can be solved with the present methods as also shown in the preferred embodiment.

[0034] The syngas injection temperature through the shaft should be about 950°C but not exceed 1050°C in order not to melt the material within the furnace,

[0035] In embodiments wherein the stream of syngas to be fed through the shaft is produced by a reforming plant comprising at least one reformer with a high temperature level (i.e. typically above the temperature level for shaft injection), H2 can advantageously be added to the stream of hot syngas downstream of the at least one reformer. The stream of H2 acts thus as a coolant of the stream of syngas. Using the hydrogen in this way, i.e. as a coolant, completely eliminates the need of heating the hydrogen prior to its injection through the shaft of the blast furnace in an expensive heating device. Indeed, the excess heat of the syngas will advantageously be used for the heating of the hydrogen. This allows to increase the efficiency of the process by eliminating both the need for syngas cooling and hydrogen heating.

[0036] Additionally, using the hydrogen in this configuration allows for higher workable hydrogen injection rates in the blast furnace, because the hydrogen is heated in the reformer and injected as part of the syngas at the shaft level. In other words, a single hot gas injection system is needed to perform both the injection of the syngas and of the hydrogen, there is no need for a separate system for heating the hydrogen to shaft level injection temperatures.

[0037] Moreover, whereas in other industries the pressure level of the reformers are relatively high, mostly above 20 barg or even above 40 barg, in a blast furnace application the required pressure level is 1 ,5 to 6 barg only. This has an important impact on the operating conditions and limits of the reforming equipment such as carbon formation and equilibrium conversion. Whereas the lower pressure level will favor a higher methane conversion at the same temperature level, it unfortunately also favors the formation of carbon soot. This is the reason for which the addition of a stream of hh to the stream of blast furnace gas and/or to the hydrocarbon containing gas upstream of the reformer is specifically advantageous as it partially suppresses soot formation, even if it simultaneously lowers the conversion of methane at a given temperature in comparison without hydrogen addition.

[0038] Hydrogen may also be added to both the hydrocarbon containing gas and/or the stream of blast furnace gas upstream of the reformer and to the stream of syngas to be injected at the shaft level. Addition of hydrogen needs to be equilibrated between its utilisation as coolant of the stream of syngas to be fed through the shaft and its addition to the hydrocarbon containing gas and/or the stream of blast furnace gas upstream of the reformer for syngas production. As already mentioned, the addition of hydrogen to the hydrocarbon containing gas and/or the stream of blast furnace gas will help to reduce the soot formation during the reforming reaction.

[0039] Another advantage of the present inventive methods for operating a blast furnace is that the hydrogen is injected either as cold hydrogen (i.e. non-heated stream heated only to temperature levels which are economically interesting) or as pure hot H2 (i.e. without CO2 and/or H2O content) thus preventing steel cracking. [0040] The main advantages and benefits of the operating method and blast furnace installation according to the disclosure can be summarized as follows:

• a reduced soot formation during the reforming process

• a reduced coke rate

• an increased auxiliary fuel injection level at the tuyere and specifically an increased injection level of hydrogen containing fuels such as hydrocarbon and/or pure hydrogen

• high CO2 savings due to replacement of a fossil fuel by hydrogen

• an improved operation of the blast furnace due to the low viscosity of H2 which prevents problems such as slipping in the shaft and improves the fluid dynamic situation of the cohesive zone with a counter flow liquid phase (molten iron and slag dropping down) / gas phase (gas flowing up) in the coke bed

• an improved hydrogen utilization in the blast furnace plant due to the blast furnace top gas recirculation resulting in a higher energy efficiency of the hydrogen utilization.

[0041] These and further advantages of the present method for operating a blast furnace, as well as the presently disclosed blast furnace installation will be further detailed below.

[0042] In embodiments, the disclosed method for operating a blast furnace further comprises the sub-steps of: a1 ) Optionally hydrogenation and/or desulfurization of the hydrocarbon containing gas and/or blast furnace gas c1 ) feeding another portion of the blast furnace gas, on its own or in a mixture with other gases, to the burners of the reformer

[0043] In such embodiments, the gas cleaning, the reforming conditions and the syngas temperature requirements could advantageously be adapted depending on the position of the addition of the hydrogen. Advantageously, H2 may be added to the stream of blast furnace gas and/or to the hydrocarbon containing gas upstream of the hydrogenation unit (before step a1 ), upstream of the reformer (before step b) and/or downstream of the reforming plant (after step c) in case that the syngas temperature is too high for its direct injection in the blast furnace.

[0044] Optionally, a stream of steam may also be added to the hydrocarbon containing gas before step a1 ), step c) and/or to the stream of blast furnace gas before step c) or to a mixture of blast furnace gas and hydrocarbon containing gas before step c).

[0045] The stream of hh and/or the stream of hydrocarbon containing gas and/or the stream of blast furnace gas might be heated, in particular any one or all of these streams may be heated prior the reforming process, preferably in a heat exchanger, the heat exchanger preferably recovering part of the energy of the flue gas coming from the reformer. Preferably, the stream of hydrocarbon containing gas and/or the stream of blast furnace gas are pre-heated (i.e. heated to a moderate temperature) upstream of the reformer. In embodiments wherein the stream of hh is added to the stream of hydrocarbon containing gas and/or the stream of blast furnace gas, the stream of hh may be pre-heated in a dedicated heating device prior to its addition to the stream of hydrocarbon containing gas and/or the stream of blast furnace gas. Alternatively, the stream of hh may be pre-heated simultaneously with the stream of hydrocarbon containing gas and/or the stream of blast furnace gas after the addition. However, in embodiments wherein the stream of H2 is added to the stream of syngas downstream of the reformer, the stream of H2 is preferably not heated or only to temperature levels which are economically interesting, i.e. for example temperature levels not requiring costly precautions against high temperature hydrogen attack, typically below 600°C or even below 400°C. In the context of the present disclosure, a non-heated stream of hydrogen or a stream of hydrogen heated only to temperature levels which are economically interesting is referred to as cold.

[0046] In embodiments, a desulfurization of the hydrocarbon containing gas may be required, depending on its composition. The removal of the sulphur, for example in a zinc oxide bed requires that the sulphur is present in an inorganic form, more specifically in the form of H2S. However, the hydrocarbon containing gas very often comprises also organic sulphur which needs to be converted in inorganic sulphur, H2S, in the presence of hydrogen and a specific catalyst. Therefore, in embodiments, it might be advantageous to add the hydrogen to the hydrocarbon gas also prior to the hydrogenation step (step a1 ) in case that a desulphurization will be required. The latter does not necessarily apply to the blast furnace gas since the blast furnace gas itself may contain sufficient hydrogen for the hydrogenation process.

[0047] Advantageously a fuel gas comprising a portion of the blast furnace gas as well as air for its respective utilisation in the burners of the at least one reformer of the reforming plant is also heated in a heat exchanger using a part of the energy of the flue gas of the reforming process.

[0048] In preferred embodiments, the stream of hh is produced by electrolysis in an electrolysis cell. Preferably, the hydrogen is renewable or “green”. In the context of the present disclosure, a renewable or “green” hydrogen means that it is preferably produced by water and/or steam electrolysis and/or that the electric power for operating the electrolysis cell is produced by a renewable source, such as wind, solar and/or hydropower.

[0049] The expression hydrocarbon or “hydrocarbon containing gas” in the context of the present disclosure means any hydrocarbon which is in gaseous state at ambient temperature. Such hydrocarbon gas thus comprises natural gas, i.e. a naturally occurring hydrocarbon gas mixture of fossil origin consisting primarily of methane and commonly including varying amounts of other higher alkanes, but also gases with similar hydrocarbon constituents, such as biogas, coke oven gas, etc. Coke oven gas is a mixture of several gases, mainly hydrogen (i.e. having a hydrogen content of at least 50%), methane (conventionally amounting for 25% of the coke oven gas) and the rest being a mixture of various gases such as nitrogen, CO, CO2 or H2O. Thus, the coke oven gas itself already contains a high amount of hydrogen.

[0050] Preferably, the hydrocarbon containing gas comprises natural gas, coke oven gas and/or biogas.

[0051] The reformer can be of any kind, such as a catalytic reformer, a regenerator type reactor also called a regenerative reformer, a reformer with plasma torches, a partial oxidation reformer, a reformer with oxygen/carbon and/or hydrocarbon burners.

[0052] Advantageously, the stream of syngas results from a dry or wet reforming process. In a so-called dry reforming process, the hydrocarbons of the hydrocarbon containing gas, such as methane, react with the CO2 in the blast furnace gas to produce H2 and CO. A dry reforming reaction is thus CPU + CO2 = 2 CO + 2 H2. In a so-called wet reforming process, the hydrocarbons react with the H2O in the blast furnace gas also to produce H2 and CO. A wet reforming reaction is thus ChU + H2O = CO + 3 H2. Either way, a syngas is obtained that has a significantly increased concentration of H2 and CO.

[0053] The reforming process can be performed either catalytically or non-catalytically. In particular, the reforming of natural gas process may be performed either catalytically or non-catalytically while the reforming of coke oven gas is preferably performed non- catalytically. A process performed catalytically is performed in the presence of a catalyst while a process performed non-catalytically is performed without a catalyst, i.e. in the absence of a catalyst. The reforming process can furthermore be performed in a single reformer or also in multiple reformers, as for example in a pre-reformer and a secondary or main reformer.

[0054] The produced syngas needs to be of high quality for its effective utilisation in the blast furnace. This quality is normally described with its reduction potential being defined as the following molar ratio: (cC0+cH₂)/(cH₂0+cC0₂). In order to ensure a sufficient quality of the syngas, the reduction potential should be as high as possible and preferably higher than six, more preferably higher than seven and most preferably higher than seven and a half.

[0055] Thermodynamically a certain degree of reduction potential of a syngas can only be achieved by applying a minimum temperature level to the reforming process. The reforming process is preferably carried out at a temperature high enough for the stream of syngas to have both a desired reduction potential and a temperature allowing its feeding through the shaft of the blast furnace. In embodiments wherein the stream of H2 is added to the hydrocarbon containing gas and/or to the stream of blast furnace gas upstream of the reformer, hydrogen addition will help to reduce the soot formation in the reformer and in the piping leading from the reformer to the blast furnace to feed the syngas through the shaft of the blast furnace.

[0056] Additionally, the stream of blast furnace gas may advantageously be subjected to a gas cooling and/or cleaning and/or pressurization step, preferably a vapor removal step, a dust removal step, metals removal step, HCI removal step and/or sulfurous component removal step, before being fed to the reformer. [0057] In embodiments, a second stream of the blast furnace gas may be used on its own, or in a mixture with other gases, in the burners of the reforming plant. In preferred embodiments, as much as possible of the blast furnace gas exiting the blast furnace is collected for its utilization in the cowper and reforming plant. In other words, the export blast furnace gas that is fed to other units within the steel plant is as small as possible. Preferably it is so low that its utilization in the thermal power plant is avoided.

[0058] The expression “in fluidic connection” means that two devices are connected by conducts or pipes such that a fluid, e.g. a gas, can flow from one device to another. This expression includes means for changing this flow, e.g. valves or fans for regulating the mass flow, compressors for regulating the pressure, etc., as well as control elements, such as sensors, actuators, etc. necessary or desirable for an appropriate control of the blast furnace operation as a whole or the operation of each of the elements within the blast furnace installation.

[0059] In the present text, “reformer” means any container in which a reforming process could be performed, such as a reformer reactor or a reformer vessel.

[0060] “Shaft feeding”, “shaft injection”, “feeding ... to the shaft of a blast furnace”, “feeding ... at the shaft level”, “feeding ... through the shaft”, “fed at the shaft level”, “injected at the shaft level” or “gas inlets in the shaft” implies the injection of a material (such as e.g. a gas) above the hot blast level, i.e. above the bosh, preferably within the gas solid reduction zone of ferrous oxide above the cohesive zone in a blast furnace.

[0061] “Feeding ... at the tuyere level”, “Feeding ... through the tuyere”, “fed at the tuyere level”, or “injected at the tuyere level” implies the injection of a material (such as e.g. a gas) through a tuyere of a blast furnace.

[0062] In the present text, “feeding to the blast furnace” and “injection to the blast furnace”, as well as “fed to the blast furnace” and “injected to the blast furnace” or “injected in the blast furnace”, are respectively used as synonym and have the same meaning, which implies the injection of a material in the blast furnace.

[0063] “Or” in the present context is not exclusive and means either “or” or “and”.

[0064] “About” in the present context means that a given numeric value covers a range of values from -10 % to +10 % of said numeric value, preferably a range of values form -5 % to +5 % of said numeric value. [0065] In the present text, step (c) refers to reforming in general. It covers producing syngas for injection through either the shaft or the tuyere, and also producing syngas for simultaneous injection through shaft and tuyere.

[0066] Further details and advantages of the present disclosure will be apparent from the following detailed description of several not limiting embodiments with reference to the attached drawings.

Brief Description of the Drawings

[0067] Preferred embodiments of the disclosure will now be described, by way of example, with reference to the accompanying drawings in which:

Fig. 1 is a schematic view of an embodiment of a first variant of a blast furnace plant configured to implement the present blast furnace operating method;

Fig. 2 is a schematic view of an embodiment of a second variant of a blast furnace plant configured to implement the present blast furnace operating method;

Fig. 3 is a schematic view of an embodiment of a third variant of a blast furnace plant configured to implement the present blast furnace operating method; and

Fig. 4 is a graph showing the variation of C₂FI₄ concentration in a reformer as a function of the temperature for various hydrogen content.

Description of Preferred Embodiments

[0068] CO2 emissions:

[0069] Coke is the main energy input in the blast furnace iron making. From the CO2 and often also from the economic point of view, this is the less favorable energy source. Substitution of coke by other energy sources, mostly injected at tuyere level, is widely employed. Due to cost reasons mostly pulverized coal is injected, however in countries with low natural gas price, this energy is used. Often residues like waste plastics are also injected in the blast furnace. In an ambition of reduction of greenhouse gas emissions, industrial operations start to incorporate also hydrogen in their auxiliary fuels and with the expected higher availability of hydrogen it is expected that the contribution of hydrogen as auxiliary fuel will strongly increase.

[0070] These auxiliary fuels may have a positive impact on the CO2 emissions from the blast furnace steel making, meanwhile their utilization is limited to process reasons and very often these limits are already reached today. The blast furnace produces blast furnace gas (BFG), which contains up to approximately 40 % of the energy input to the blast furnace. About 25% of that blast furnace gas leaving the blast furnace is normally used in the cowper plant for heating of the blast that is injected at the tuyeres of the blast furnace. The remaining 75% of that blast furnace gas, containing about 30% of the energy input to the blast furnace is generally used for internal heat requirements in the steel plant, but also for electric energy production.

[0071] For the objective of reducing the CO2 footprint of a blast furnace-based steel production, one important strategy is thus to use as much as possible of this BFG for metallurgical purposes and apply other CO2 lean energies such as green electric energy for the remaining energy requirement of the steel plant.

[0072] Flence, the synthesis gas production should, beside the utilization of a CO2 lean hydrocarbon, also use blast furnace gas as much as possible in order to improve the CO2 emission reduction potential from the blast furnace iron making, as well as, if available in the blast furnace plant, converter gas and/or cold basic oxygen furnace (BOF) gas.

[0073] Flydrogen utilization for iron making:

[0074] The hydrogen utilization for iron making can be divided in the direct utilization of the hydrogen in the blast furnace as well as its utilization in the auxiliary plants, specifically the cowper plant and if installed the reforming plant for the production of the syngas to be injected in the shaft of the blast furnace.

[0075] The utilization of hydrogen in the blast furnace is generally referred to as the eta H2. Eta H2 being defined as: eta H2 = ((H2 in BF) - (H2 out BF in top gas)) / (H2 in BF). In the present text, BF means blast furnace, so that (H2 in BF) refers to the flow of H2 going into the blast furnace, and (H2 out BF in top gas) refers to the flow of H2 in the blast furnace top gas exiting the top of the blast furnace.

[0076] “H2 in BF” is defined as the total hydrogen content of the bosh gas (i.e. gas in the cohesive zone of the blast furnace) and of the shaft gas injected to the blast furnace at shaft level. This hydrogen input to the blast furnace includes in particular the hydrogen contained in the syngas, in the injected molecular hydrogen H2, in the other hydrogen containing gases, in the injected coal and/or tar, in the humidity of the injected gases and solid fuels and the humidity of the hot blast.

[0077] “Fh out BF in top gas” is defined in the dry flow rate of the top gas leaving the blast furnace times the dry concentration of hydrogen in that top gas.

[0078] The eta Fh is normally below 50% and often below 45%. The eta Fh, and thus the percentage of hydrogen utilisation in the blast furnace, has furthermore the characteristic that it decreases with increasing hydrogen input into the blast furnace. This means when one wants to use more hydrogen in the blast furnace, the efficiency of its utilisation strongly decreases and a much bigger portion of the hydrogen introduced in the blast furnace is leaving it with the top gas. In consequence also the attainable coke rate reduction per kg of injected hydrogen decreases which indirectly reduces the CO2 reduction potential of the injected hydrogen.

[0079] Moreover, when increasing the injection of auxiliary fuel (i.e. hydrogen containing gas), the enrichment of oxygen must be increased in order to maintain the flame temperature. Increasing the oxygen enrichment in the blast furnace signifies reducing the amount of natural blast (air) that will be used in the blast furnace. In consequence the overall amount of hot blast entering the blast furnace is decreased. This means that less blast furnace gas can be used for heating the hot blast.

[0080] This finally means that when increasing the percentage of hydrogen in the blast furnace for the reduction of iron ore, a smaller part of this hydrogen is used within the blast furnace and a smaller part of it is used in the cowper plant resulting in an increased amount of hydrogen leaving the blast furnace plant in the export gas.

[0081] This is shown in the following table (Table 1) which is comparing a reference operation of a blast furnace and operation of a blast furnace with hydrogen injection according to three embodiments of the present inventive method. [Table 1]

[0082] In the reference operation, the blast furnace uses only coke and pulverised coal injection at the tuyere, whereas in case 1 , cold hydrogen is additionally injected at the tuyere level of the blast furnace.

[0083] One can see in case 1 , that the ratio of the export hydrogen from the blast furnace plant increases by 4.487 Nm³ from 10.045 Nm³/h (for the reference) to 14.532 Nm³/h (for case 1 ) for an increase of the hydrogen input in the blast furnace by 11 .198 Nm³ from 30.322 (for the reference) to 41.520 Nm³/h (for case 1 ). This results in a decrease of the hydrogen utilisation in the blast furnace plant from 67 to 65%. In other words, the 4.487 Nm³ that leave the blast furnace plant in the top gas represent 40% of the additional injected hydrogen of 11.198 Nm3, thus the utilisation of the additional hydrogen in the blast furnace is much lower and 60% only.

[0084] In case 2 (Table 1 ) a hot syngas is injected at the shaft of the blast furnace at 950°C. One can see now even though that the total amount of hydrogen injected in the blast furnace is more than tripled in comparison to the reference case, its utilisation in the blast furnace plant is increased from 67 to 69%. This is very impressive since this shows that only a small addition of hydrogen to the blast furnace at the tuyere level already impacts in decreasing the utilisation of the hydrogen in the blast furnace plant. Compared to the reference case, the additional injection of 72.703 Nm³ of hydrogen, only 21 627Nm³ or 30% are leaving the blast furnace plant with the export gas.

[0085] In the last case shown in Table 1 (case 3), the amount of hydrogen entering the blast furnace was considerably increased, i.e. more than quadrupled compared to the reference case. Even now one can see that the utilisation of the hydrogen within the blast furnace plant is higher as in the reference case. Out of the additional injection of 94.984 Nm³ of hydrogen, only 30.304Nm³ or 32% are leaving the blast furnace plant with the export gas.

[0086] Energy efficiency

[0087] In order to achieve an overall high efficiency of the process, the cowper plant as well as the reforming plant shall preferably be equipped with heat recovery systems for preheating the combustion air and/or combustion gas. The efficiency of both plants should be above 70%, more specifically above 80%.

[0088] Reforming and syngas requirements:

[0089] The requirements for the syngas for its utilization in the blast furnace are different to the requirements for applications in other industries.

[0090] The main requirements for syngas utilization in the blast furnace are as follows:

[0091] Reduction potential and temperature level of the syngas:

[0092] In other industries the syngas is normally produced and then cooled to separate the excess of steam from the syngas. Thereby only cooled gas is used in the downstream processes. In existing industrial applications beside the steel industry, a high reduction potential directly achieved by the reforming process is therefore not important. In the steel industry however a high reduction potential, preferably as high as possible and at least above 6, is preferable and highly advantageous for a high process efficiency, the reduction potential, or reduction degree, being defined as: (CC0+CH₂)/(CH₂0+CC0₂), where c means the molar concentration, such that e.g. cCO means the molar concentration of CO in the syngas, cH₂ means the molar concentration of H₂ in the syngas, cH₂0 means the molar concentration of H₂0 in the syngas and cC0₂ means the molar concentration of C0₂ in the syngas.

[0093] Furthermore, high temperatures of syngas are favoured and compatible to the temperature level required for shaft injection through the tuyere and/or through the shaft in order to allow maximum thermal efficiency. Thus, the temperature should be between 850 to 1100°C, preferably about 950°C, to allow its injection in the shaft above the cohesive zone of a blast furnace, i.e. at the shaft level. [0094] Ratio H2/CO:

[0095] In the other industries, beside steel industry, the syngas is used for specific applications, such as pure hydrogen production, ammonia or the production of other chemical components. Thereby a specific ratio of hydrogen to CO within the syngas is generally required.

[0096] In comparison, the object of using syngas in a blast furnace is the reduction of ore, which is achieved with both reducing components, CO and hydrogen. While there is a difference between the reduction of ore with CO or hydrogen, this difference is relatively marginal considering that syngas is only one part of the reducing gas used within the blast furnace.

[0097] Pressure level:

[0098] Whereas in other industries the pressure levels of the reformers are relatively high, mostly above 20 barg or even above 40 barg, in the blast furnace application the required pressure level is 1 ,5 to 6 barg only. This has an important impact on the operating conditions and limits of the reforming equipment such as soot formation and equilibrium conversion. Whereas the lower pressure level will favor a higher methane conversion at the same temperature level, it unfortunately also favors the formation of soot, reason for which the addition of a stream of H2 to the stream of blast furnace gas and/or to the hydrocarbon containing gas upstream of the reformer is specifically advantageous to partially suppress soot formation, even if it simultaneously lowers the conversion of methane at a given temperature in comparison without hydrogen addition.

[0099] Hydrogen addition:

[00100] As already shown above the hydrogen can simply be added at the tuyere of the blast furnace, in form of H2 and also in the form of hydrocarbon. However, it is possible to also use the hydrogen addition to positively impact the syngas production and its injection at the shaft of the blast furnace.

[00101] A stream of hydrogen, preferably renewable hydrogen, is added to the method, in particular before the reformer, reducing soot formation or after the reformer to the stream of syngas to be injected through the shaft in order to simultaneously cool it down and increasing its reduction potential. In the present text, and when referring to the syngas, reduction potential and reduction degree are used as synonym for one another and both refers to the molar ratio (cC0+cH2)/(cH20+cC02). Before addition of hydrogen upstream of the reformer, it may be beneficial to heat the stream of hydrogen.

[00102] Reforming reactions for syngas production:

[00103] Hydrocarbon gas reforming, such as natural gas reforming can principally be performed by following reactions:

[00104] Steam reforming in the presence of steam: CH₄ + H₂0 = CO + 3 H₂

[00105] Dry reforming in the presence of CO2: CH₄ + C0₂ = 2 CO + 2 H₂

[00106] These two reactions are strongly endothermic and require a lot of heat.

[00107] This heat can be supplied indirectly by burning a fuel gas and transferring the flue gas heat to the reactor, or also by combining the reforming reaction with a partial oxidation reaction according the below formula:

[00108] CH₄ + ½ 0₂ -> CO + 2H₂

[00109] Along the reforming reactions, side reactions can occur in the reformer. The relative importance of these reactions depends on the operating conditions such as gas composition, temperature and pressure, use and nature of catalysts and the like. The main side reactions at temperatures close to the reforming temperature are:

[00110] Reverse water-gas shift reaction (RWGS): CO + H₂0

[00111] CH₄ decomposition: CH₄ -> C + 2H₂

[00112] Methanation reaction 4H2 + CO2 -> CH₄ + 2H2O or 3H2 + CO -> CH₄ + H2O

[00113] As well as the multitude of reactions that are part of the reaction scheme for the production of soot / carbon deposit. Exemplarily for those reactions is the formation of acetylene, as shown below:

[00114] Formation of acetylene: 2CH₄ -> C2H2 + 3H₂

[00115] This acetylene can then be a molecule (precursor) in the creation of aromatic hydrocarbons which are part of the soot or can be thermally decomposed according to following reaction:

[00116] Decomposition of acetylene: C2H2 -> 2C + H2 [00117] Hydrogen is part of most of these reactions and will thus have an important impact on the reforming reaction itself but also on the side reactions. It is therefore possible to take advantage of the desired utilization of hydrogen in the blast furnace for CO2 reduction purposes to further improve the hydrocarbon reforming process, such as to reduce the soot formation and deposition, by adding H2 to the stream of blast furnace gas and/or the hydrocarbon containing gas upstream of the reformer.

Detailed description of three different embodiments of the invention

[00118] In the following, three different variants of the method for operating a blast furnace and the blast furnace plant are shown in relation with the annexed drawings.

[00119] Fig. 1 illustrates an embodiment of a first variant of the present method for operating a blast furnace comprising the simultaneous injection of a first stream of syngas through the shaft of a blast furnace and of a second stream of syngas through the tuyere of the blast furnace.

[00120] Blast furnace gas 10 exiting the blast furnace 12 is collected at the top of a blast furnace 12.

[00121] The collected blast furnace gas 10 is generally pre-treated upon exiting the blast furnace. Pre-treatment of the stream of blast furnace gas comprises first a cooling to reduce its vapor content, a cleaning, in particular a removing of dust and/or HCI and/or metal compounds, and then a pressurization to have a pressure sufficient for an eventual desulphurization, the heating, the reforming process and injection in the blast furnace. In the embodiment of Fig.1 , the cooling, cleaning and pressurization of the blast furnace gas occurs in a cooling, cleaning and pressuring unit 14. Alternatively, separate units could be used, each unit performing either one of cooling, cleaning or pressuring the blast furnace gas. In other embodiments, one unit may be responsible for two of cooling, cleaning and pressuring the blast furnace gas, the third pre-treatment step being performed in a separate unit. In the present text, a cooling, cleaning and pressuring unit is a unit configured to cool, clean and pressurize a stream of gas, without assuming that it is mandatory to perform the various steps (cooling, cleaning and pressuring) in this order. In embodiments, the pressurization can take place upstream of the cleaning, such as e.g. in embodiments wherein the cleaning of the stream of gas is a desulphurization. [00122] Downstream of the cooling, cleaning and pressuring unit 14, the stream of blast furnace gas is split in three streams. A first stream of blast furnace gas 16 is fed to a first reforming plant 18 and a second stream of blast furnace gas 20 is fed to a second reforming plant 22. In the present embodiment, both reforming plants are regenerative type reforming plants. A third stream of blast furnace gas 27 is referred to as blast furnace export gas and corresponds to blast furnace gas being fed to another unit of a steel making plant comprising the blast furnace plant with the reforming plants 18, 22.

[00123] Additionally, a stream 24 of coke oven gas and/or natural gas is fed to the reforming plants 18, 22.

[00124] Basic oxygen furnace gas and/or steam might optionally be added to the stream of blast furnace gas (upstream and/or downstream of the cooling, cleaning and pressuring unit 14) and/or the stream of hydrocarbon containing gas 24 and/or directly to a reforming plant 18, 22 (not shown).

[00125] A reforming of the first stream of blast furnace gas 16 along with the stream 24 of coke oven gas and/or natural gas is done in the first reforming plant 18 to produce a first stream of syngas 26. A reforming of the second stream of blast furnace gas 20 along with the stream 24 of coke oven gas and/or hydrocarbon containing gas is done in the reforming plant 22 to produce a second stream of syngas 28.

[00126] Both reforming processes are dry and/or wet reforming processes, possibly also in combination with a partial oxidation, leading to the formation of two streams of syngas 26, 28 with high CO and hh contents. Reforming processes occurs at pressure between 1 ,5 and 10 barg and depending on the reforming plant at a temperature above 900 °C, preferably above 950 °C, more preferably above 1000 °C.

[00127] Blast furnace gas and/or hydrocarbon containing gas might optionally be heated prior to the reforming process (not shown). Heating might be performed e.g. by using tube bundle heat exchangers. The second stream of syngas 28 exiting the second reforming plant 22 is fed to the blast furnace through the tuyere 30 with a temperature of about 1200 °C and a pressure of 2 to 6 barg.

[00128] Additionally, the blast furnace installation comprises an electrolysis cell 32 fueled by electrical power 34 to produce a stream of H236 by electrolysis, preferably by water/steam electrolysis. The electrical power 34 fueling the electrolysis cell 32 is preferably renewable or “green”, i.e. obtained from a renewable source such as wind, solar and/or hydropower.

[00129] Alternatively or additionally, said hydrogen can be produced from natural gas through a pyrolysis process with solid carbon formation, or with combined Carbon Capture and Storage (CCS) technology and/or Carbon Capture and Utilization (CCU) technology. Hydrogen might also be produced by methane thermal cracking or steam methane reforming with combined CCS and/or CCU technology.

[00130] The stream of H236 produced by the electrolysis cell is added to the first stream of syngas 26 downstream of the first reforming plant 18 and upstream of gas inlets 38 disposed through the shaft inside the blast furnace 12. The first stream of syngas 26 added with hydrogen 36 form a stream of H2-enriched gas 40, which is fed to the blast furnace through the gas inlets 38 at the shaft level, with a temperature of about 900°C and a typical pressure of 1 ,5 to 4 barg.

[00131] The stream of H2 36 acts as a coolant of the first stream of syngas 26. Using said hydrogen in this way, i.e. as a coolant, completely eliminates the need of heating said hydrogen prior to its injection through the shaft of the blast furnace 12 in an expensive heating device. Indeed, the excess heat of the syngas 26 heats said hydrogen. This allows to increase the efficiency of the process by eliminating both the need for syngas cooling and hydrogen heating.

[00132] Fig. 2 illustrates an embodiment of a second variant of the present method for operating a blast furnace comprising the simultaneous injection of a first stream of syngas through the shaft of a blast furnace and of a second stream of syngas through the tuyere of the blast furnace.

[00133] Blast furnace gas 110 exiting the blast furnace 112 is collected at the top of a blast furnace 112.

[00134] The collected blast furnace gas 110 is generally pre-treated upon exiting the blast furnace. Pre-treatment of the stream of blast furnace gas comprises first a cooling to reduce its vapor content, a cleaning, in particular a removing of dust and/or HCI and/or metal compounds and/or sulfurous components, and then a pressurization to have a pressure sufficient for the reforming process and its injection in the blast furnace. In the embodiment of Fig. 2, the cooling, cleaning and pressurization of the blast furnace gas occurs in a cooling, cleaning and pressuring unit 114. Alternatively, separate units could be used, each unit performing either one of cooling, cleaning or pressuring the blast furnace gas. In other embodiments, one unit may be responsible for two of cooling, cleaning and pressuring the blast furnace gas, the third pre-treatment step being performed in a separate unit.

[00135] Downstream of the cooling, cleaning and pressuring unit 114, the stream of blast furnace gas is split in three streams. A first stream of blast furnace gas 116 is fed to a first reforming plant 118 and a second stream of blast furnace gas 120 is fed to a second reforming plant 122. In the present embodiment, both reforming plants are regenerative type reforming plants. A third stream of blast furnace gas 127 is referred to as blast furnace export gas and corresponds to blast furnace gas being fed to another unit of a steel making plant comprising the blast furnace plant with the reforming plants 118, 122.

[00136] Additionally, the blast furnace installation comprises, in addition to the blast furnace and the cooling, cleaning and pressuring unit 114, a source for a stream 124 of coke oven gas and/or natural gas in fluidic communication with each of the reforming plants 118, 122, and an electrolysis cell 132 fueled by electrical power 134 to produce a stream of hh 136 by electrolysis, preferably by water electrolysis. The electrical power 134 fueling the electrolysis cell 132 is preferably renewable or “green”, i.e. obtained from a renewable source such as wind, solar and/or hydropower.

[00137] The stream of hh 136 produced by the electrolysis cell is added to the stream 124 of coke oven gas and/or natural gas upstream of the reforming plants 118, 122 to form a stream of hh-enriched hydrocarbon containing gas 142, which is fed to each of the reforming plants 118, 122.

[00138] Basic oxygen furnace gas and/or steam might optionally be added to the stream of blast furnace gas (upstream and/or downstream of the cooling, cleaning and pressuring unit 114) and/or the stream of hydrocarbon containing gas 124 and/or to the stream of hh 136 and/or directly to a reforming plant 118, 122 (not shown).

[00139] A reforming of the first stream of blast furnace gas 116 along with the stream of hh-enriched hydrocarbon containing gas 142 is done in the first reforming plant 118 to produce a first stream of syngas 126. A reforming of the second stream of blast furnace gas 120 along with the stream of hh-enriched hydrocarbon containing gas 142 is done in the second reforming plant 122 to produce a second stream of syngas 128.

[00140] Both reforming processes are dry reforming, leading to the formation of two streams of syngas 126, 128 with high CO and hh contents. Reforming processes occurs at pressure between 1 ,5 and 10 barg and depending on the reforming plant at temperatures above 900 °C, preferably 1000 °C, more preferably above 1200 °C.

[00141] Blast furnace gas and/or hydrogen containing gas might optionally be heated prior to the reforming process (not shown). Heating might be performed e.g. by using tube bundle heat exchangers.

[00142] The addition of hydrogen to the hydrocarbon containing gas upstream of the reforming plants 118, 122, and thus prior to the reforming processes, will help to reduce the soot formation during the reforming reaction. The formation of carbon deposits through the dry reforming is a known problem. There are different reactions occurring inside the reforming plant and leading to the formation of carbon deposits. A high number of such reactions include the formation of ethene C2H4 and acetylene C2H2 precursors. The formation of these precursors from methane leads to a separation of hydrogen and an increase in the gas volume. It is thus possible to reduce the formation of the carbon deposit precursors and thereby the formation of the carbon deposit itself by increasing the partial pressure of hydrogen in the reactor inlet gas, which means adding H2 to the gas mixture to be reformed, such as by adding H2 to the hydrocarbon containing gas and/or to the stream of syngas. For example, as shown on Fig. 4, increasing the amount of H2 in the gas mixture to be reformed from 10% to 40% leads to a significant decrease of the C2H4 concentration in the reforming plant, from about 0.35% to about 0% at 1225 °C.

[00143] The first stream of syngas 126 exiting the second reforming plant 118 is fed to the blast furnace through gas inlets 138 disposed through the shaft inside the blast furnace 112 (i.e. the second stream of syngas 126 is fed through the shaft of the blast furnace) with a temperature of about 950 °C and a pressure of 1 ,5 to 4 barg. Depending on the reforming process, the second stream of syngas may be cooled prior to being fed through the shaft of the blast furnace to a temperature of about 950 °C. [00144] The second stream of syngas 128 exiting the second reforming plant 122 is fed to the blast furnace through the tuyere 130 with a temperature of about 1200 °C and a pressure of 2 to 6 barg.

[00145] Fig. 3 illustrates a third embodiment of the present method for operating a blast furnace comprising the simultaneous injection of a first stream of syngas through the shaft of a blast furnace together with the injection of a cold hydrogen and/or a hydrocarbon containing gas and possibly also pulverized coal through the tuyere of the blast furnace.

[00146] Blast furnace gas 210 exiting the blast furnace 212 is collected at the top of a blast furnace 212.

[00147] The collected blast furnace gas 210 is generally pre-treated in a gas cleaning and cooling unit 214 upon exiting the blast furnace. Pre-treatment of the stream of blast furnace gas comprises first a cooling to reduce its vapor content, a cleaning, in particular a removing of dust and/or HCI and/or metal compounds.

[00148] Part of the cleaned blast furnace gas 219 is used as part of the fuel, along with humid air 223, and often along with other high calorific gases (not shown) in the burners of the cowper plant 221 for heating of the blast that is injected in the blast furnace at its tuyere level. Both, gases and air may be preheated or not.

[00149] Another part of the blast furnace gas 217 is used as part of the fuel, along with humid air 223, and often along with other high calorific gases (not shown) in the burners of the reforming plant 218. Both gases and air may be preheated or not.

[00150] Another stream 216 of the blast furnace gas is used within the reforming reaction. This stream is further fed to a compressor (pressuring unit) 215 for compressing the blast furnace gas to the required pressure level for reforming and injection in the blast furnace.

[00151] Remaining blast furnace gas exiting the blast furnace 212 and not being used in either the reforming plant or the cowper plant is referred to a blast furnace export gas 227 and is fed to other units within a steel plant comprising the blast furnace 212.

[00152] In the embodiment of Fig. 3, there is optionally also a hydrogenation and desulphurization unit 250 after the compressor (pressuring unit) 215. [00153] Additionally, a stream 224 of coke oven gas and/or natural gas is fed to the reforming plants 218. The gas 224 can be desulphurized in the desulphurization unit 250. Desulphurization of the gas 224 can be performed along desulphurization of blast furnace gas (Fig.3). Alternatively, the gas 224 can be desulphurized in a separate desulphurization unit (not shown). In such embodiments, hydrogen may be added to natural gas for the hydrogenation of organic sulphur contained in the natural gas (not shown).

[00154] Basic oxygen furnace gas and/or steam 225 might optionally be added to the stream of blast furnace gas (upstream and/or downstream of the pressuring unit 215), to the hydrogenation and desulphurization unit 250, to the stream of hydrocarbon containing gas 224 (not shown) and/or directly to a reforming plant 218 or after the reforming plant 224.

[00155] The reforming of the stream of blast furnace gas 216 along with the stream 224 of coke oven gas and/or natural gas is done in the reforming plant 218 to produce a stream of syngas 226. The two gas streams of blast furnace gas 216 and hydrocarbon containing gas need to be mixed prior entering the reforming plant 218, within the reforming plant 218 and/or prior to entering the hydrogenation and desulphurization plant 250.

[00156] The reforming processes are dry and/or wet reforming processes, possibly also in combination with a partial oxidation, leading to the formation of a stream of syngas 226, with high CO and Fh contents. Reforming processes occurs at pressure between 1 ,5 and 10 barg and depending on the reforming plant at a temperature above 900 °C, preferably above 950 °C, more preferably above 1000 °C.

[00157] Blast furnace gas and/or hydrogen containing gas may optionally be heated prior to the reforming process (not shown). Heating might be performed e.g. by using tube bundle heat exchangers transferring part of the heat of the flue gas from the reforming plant. The same applies to the gas mixture comprising blast furnace gas and hydrocarbon containing gas entering the reforming plant, which will preferably also be heated to at least 350°C, more preferably to above 400°C and preferred to above 450°C. Optionally, blast furnace gas and air used in the burners of the cowper plant and/or of the reforming plant may also be heated transferring part of the heat of the flue gas from the reforming plant in heat exchangers e.g. as tube bundle heat exchanger. [00158] Additionally, the blast furnace installation comprises an electrolysis cell 232 fueled by electrical power 234 to produce a stream of hh 236 by electrolysis, preferably by water/steam electrolysis. The electrical power 234 fueling the electrolysis cell 232 is preferably renewable or “green”, i.e. obtained from a renewable source such as wind, solar and/or hydropower.

[00159] Alternatively or additionally, said hydrogen can be produced from natural gas through a pyrolysis process with solid carbon formation, or with combined Carbon Capture and Storage (CCS) technology and/or Carbon Capture and Utilization (CCU) technology. Hydrogen might also be produced by methane thermal cracking or steam methane reforming with combined CCS and/or CCU technology.

[00160] The stream of H2236 produced by the electrolysis cell, or a part of it, is added to the stream 224 of coke oven gas and/or natural gas upstream of the reforming plant 218 to form a stream of H2-enriched hydrocarbon containing gas, which is fed to the reforming plant 218 and / or a part of it is fed to the stream of hydrocarbon containing gas prior to the hydrogenation step and/or is fed cold at the tuyere of the blast furnace on its own or together with other auxiliary fuels such as coal, natural gas, plastics, biomass and the like.

[00161 ] Basic oxygen furnace gas and/or steam might optionally be added to the stream of blast furnace gas (upstream and/or downstream of the pressuring unit 215 or the hydrogenation unit 250) (not shown) and/or the stream of hydrocarbon containing gas 224 (not shown) and/or to the stream of H2 236 (not shown) and/or directly to the reforming plant 218 or after the reforming plant 218.

[00162] Part of the stream of H2 236 may be added to the stream of syngas 226 downstream of the reforming plant 218 and upstream of gas inlets 238 disposed through the shaft inside the blast furnace 212. The stream of syngas 226 added with hydrogen 236 form a stream of H2-enriched gas 240, which is fed to the blast furnace through the gas inlets 238 at the shaft level, with a temperature of about 900°C and a typical pressure of 1 ,5 to 4 barg.

[00163] Part of the Hydrogen 236 and/or hydrocarbon containing gas 224 may also be directly injected through the tuyere 230 of the blast furnace. In embodiments, injection of hydrogen 236 and/or hydrocarbon containing gas 224 may be performed along with injection of solid fuels, such as e.g. pulverized coal injection 229. [00164] Part of the stream of hh 236 may be used as a coolant of the first stream of syngas 226. Using said hydrogen in this way, i.e. as a coolant, completely eliminates the need of heating said hydrogen prior to its injection through the shaft of the blast furnace 212 in an expensive heating device. Indeed, the excess heat of the syngas 226 heats said hydrogen. This allows to increase the efficiency of the process by eliminating both the need for syngas cooling and hydrogen heating.

[00165] While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. Other variations to be disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

List of reference numbers

Claims

1. A method for operating a blast furnace (12, 112, 212), comprising the steps of a. collecting a stream of blast furnace gas (16, 116, 216) from a blast furnace (12, 112, 212) having a shaft and at least one tuyere; b. feeding said stream of blast furnace gas (16, 116, 216) and a hydrocarbon containing gas (24, 124, 224) to a reforming plant comprising at least one reformer (18, 118, 218); c. reforming said stream of blast furnace gas (16, 116, 216) and said hydrocarbon containing gas (24, 124, 224) in the reforming plant (18, 118, 218) to produce a stream of syngas (26, 126, 226); and d. feeding at least a portion of said stream of syngas (26, 126, 226) to the blast furnace (12, 112, 212); wherein a stream of hh (36, 136, 236) is added to the hydrocarbon containing gas (24) before step (c) and/or to the stream of blast furnace gas (16) before step (c) and/or to a mixture comprising the blast furnace gas and the hydrocarbon containing gas before step (c) and/or to the stream of syngas (26) before step (d), and wherein the feeding of at least a portion of said stream of syngas (26) to the blast furnace occurs through the shaft (38) of the blast furnace.

2. A method for operating a blast furnace (212), by improving the efficiency of hydrogen utilisation in a blast furnace (212), the method comprising the combination of hh addition to the blast furnace, with a reforming reaction, wherein the part of hydrogen utilization in a blast furnace plant comprising the blastfurnace (212), a reforming plant (218) and a cowper plant (221) is above 60% of the hydrogen fed to the blast furnace and preferably above 65% of the hydrogen fed to the blast furnace, wherein the hydrogen utilization is defined as: (hydrogen input to the blast furnace plant - hydrogen export from the blast furnace plant) / (hydrogen input to the blast furnace plant), wherein the hydrogen fed to the blast furnace is defined as the total hydrogen content of the gas in a cohesive zone of the blast furnace and of the shaft gas injected to the blast furnace at shaft level (240) and the hydrogen fed to the blast furnace is totaling a flow of minimum 200 Nm³/t of produced hot metal and out of which a minimum of 50Nm³ / 1 of hot metal are fed to the blast furnace plant in form of molecular hydrogen hh (236), wherein the hydrogen input to the blast furnace includes in particular the hydrogen contained in the syngas (226), in the injected molecular hydrogen H2 (236), in the other hydrogen containing gases (224), in the injected coal and/or tar, in the humidity of the injected gases (224) and solid fuels (229) and in the humidity of the hot blast (230).

3. The method as claimed in claim 1 , wherein the feeding of at least a portion of said stream of syngas (26) to the blast furnace occurs through the shaft (38) of the blast furnace and through the at least one tuyere (30) of the blast furnace.

4. The method as claimed in claim 1 , 2 or 3, wherein at least a part of the hydrogen fed to the blast furnace plant is injected through the tuyere of the blast furnace.

5. The method according to any of the preceding claims, wherein the feeding of at least a portion of said stream of syngas (26) to the blast furnace occurs through the shaft (38) of the blast furnace and through the tuyere (30) of the blast furnace.

6. The method according to any of the preceding claims, wherein the stream of H2 (36, 236) is added to the stream of syngas (26, 226) with a temperature below 600°C.

7. The method according to any one of the preceding claims, wherein the stream of blast furnace gas and/or the stream of hydrocarbon containing gas is hydrogenated and/or desulphurised in a hydrogenation and desulphurization unit (250) upstream of the reforming plant (218).

8. The method according to claim 7, wherein at least part of the hydrogen is added to the stream of hydrocarbon containing gas upstream of the hydrogenation and desulphurization unit (250).

9. The method as claimed in any one of the preceding claims, wherein the stream of H2 (36) is produced by electrolysis in an electrolysis cell (32).

10. The method as claimed in claim 9, wherein an electric power (34) for operating the electrolysis cell (32) is produced by a renewable source, such as wind, solar and/or hydropower.

11. The method as claimed in any one of the preceding claims, wherein the hydrocarbon containing gas (24) comprises natural gas, coke oven gas and/or biogas.

12. The method as claimed in any one of the preceding claims, wherein the at least one reformer of the reforming plant (18) is a regenerative reformer.

13. The method as claimed in any one of the preceding claims, wherein the at least one reformer of the reforming plant (18) is a catalytic dry and/or wet reformer of any type, in particular bottom fired, side fired, terrace type or top fired.

14. The method as claimed in any one of the preceding claims, wherein the reforming plant (18) comprises two reformers, in particular a pre-reformer and a main reformer.

15. The method as claimed in any one of the preceding claims, wherein the reforming at step (c) is performed non-catalytically.

16. The method as claimed in any one of the preceding claims, wherein the reforming at step (c) is combined with a partial oxidation of hydrocarbons.

17. The method as claimed in any one of the preceding claims, wherein a reduction potential of the syngas (26, 28) produced at step (c) is higher than 6, preferably higher than 7, more preferably higher than 7,5, wherein the reduction potential is defined by the molar ratio (cC0+cH2)/(cH20+cC02).

18. The method as claimed in any one of the preceding claims, wherein the reforming at step (c) is performed at a temperature above about 900 °C, preferably above about 950 °C, more preferably above about 1000 °C.

19. The method as claimed in any one of the preceding claims, wherein the stream of blast furnace gas (10) is further subjected to a gas cooling and/or cleaning and/or pressurization step, preferably a vapor removal step, a dust removal step, metals removal step, HCI removal step and/or sulfurous component removal step, before being fed to the reformer (18).

20. The method as claimed in any of the preceding claims, wherein a stream of steam is added to the hydrocarbon containing gas (24) and/or a stream of steam is added to the blast furnace gas after the cleaning step.

21. The methods as claimed in any of the preceding claims, wherein a stream of blast furnace gas is used in the burners of the reforming plant.

22. A blast furnace plant comprising a blast furnace (12, 112, 212) provided with a shaft, tuyeres arranged for feeding a first stream of a hydrogen containing gas to the blast furnace and gas inlets in the shaft of the blast furnace arranged for feeding a stream of syngas to the blast furnace, said blast furnace plant further comprising: a reforming plant (18, 118, 218) comprising at least one reformer in fluidic connection with the top of the blast furnace (12, 112, 212) and with a source of a hydrocarbon containing gas (24, 124, 224), said reformer being arranged for converting a stream of blast furnace gas and the hydrocarbon containing gas to a stream of syngas and being in fluidic downstream connection with said gas inlets in the shaft of the blast furnace; and a source of a stream of hh (36, 136, 236) in fluidic connection with the at least one reformer and/or with the gas inlets in the shaft and/or the tuyere of the blast furnace.

23. The blastfurnace installation as claimed in claim 22, wherein the blast furnace installation is configured for implementing the method for operating a blast furnace as claimed in any one of claims 1 to 21 .

24. The blast furnace installation as claimed in claim 22 or 23, wherein the reformer is in fluidic downstream connection with the tuyeres of the blast furnace and with the gas inlets in the shaft of the blast furnace.

25. The blast furnace installation as claimed in any one of claims 22 to 24, wherein the reforming plant (18) comprises a regenerative reformer.

26. The blast furnace installation as claimed in any one of the claims 22 to 25, wherein the reforming plant (18) comprises a catalytic dry and/or wet reformer, and/or wherein the reforming plant (18) comprises two reformers, in particular a pre-reformer and a main reformer.

27. The blast furnace installation as claimed in any one of claims 22 to 26, wherein the reforming plant (18) further comprises a partial oxidation reactor.

28. The blast furnace installation as claimed in any one of claims 22 to 27, wherein the fluidic connection with the top of the blast furnace arranged for conveying a stream of blast furnace gas to the reforming plant further comprises a gas cooling and/or cleaning and/or pressurizing plant, preferably a vapor removal unit, a dust removal unit, metals removal unit, HCI removal unit and/or sulphurous component removal unit.

29. The blast furnace installation as claimed in any one of claims 22 to 28, wherein the fluidic connection with the top of the blast furnace arranged for conveying a stream of blast furnace gas to the reforming plant further comprises a pressuring unit (215) and/or a hydrogenation and desulphurization unit (250).